Ok! I think I will need to update my JSS from 8.43 to 8.52.
Jamf Support response....

We have the variable $COMPUTERNAME for use in Configuration Profiles, which will grab the computer name.  If you're interested in checking out the other variables that we can use in configuration profiles, there is a table on page 314 of the Casper Admin's guide:

http://www.jamfsoftware.com/libraries/pdf/products/documentation/Casper_Suite_8.5_Documentation.pdf

Hi Cem,
Would you know what Subject name I can use for iOS? I tried both $COMPUTERNAME and $SERIALNUMBER in the SCEP setting in IPCU. The the iPad receive the certificate, it did not reflect it's name or serial number. I have received the certificate which looks like
$COMPUTERNAME.mycompany.com
or
$SERIALNUMBER.mycompany.com
The variables didn't work for me.
Any idea?
Thanks.

Casper Suite 8.6 Administrator's Guide.pdf Page 450

Variables for iOS Configuration Profiles
There are several variables that you can use to dynamically customize the payloads in an iOS configuration profile.
Enter a variable into any text field in a payload to dynamically populate information about the devices to which you are distributing the profile. When the profile is installed, the variable is translated to the actual value stored in the JSS.
Variable
Mobile Device Information
$UDID
UDID
$SERIALNUMBER
Serial number
$USERNAME
Username
$REALNAME
Real name
$EMAIL
Email address
$PHONE
Phone
$ROOM
Room
$POSITION
Position

Also see Casper Suite 8.6 Administrator's Guide.pdf Page 327

Variables for Mac OS X Configuration Profiles
There are several variables that you can use to dynamically customize the payloads in a Mac OS X configuration profile.
Enter a variable into any text field in a payload to dynamically populate information about the computers to which you are distributing the profile. When the profile is installed, the variable is translated to the actual value stored in the JSS.
??
Variable
Computer Information
$COMPUTERNAME
Computer name
$UDID
UDID
$SERIALNUMBER
Serial number
$USERNAME
For a computer-level configuration profile, the username stored in the computer’s location information in the JSS
For a user-level configuration profile, the username for the user logging in
$REALNAME
Real name
$EMAIL
Email address
$PHONE
Phone
$POSITION
Position
$ROOM

Hi Cem,
I have actually tried these varibles for iOS from the Adminstrator Guide. They don't actually work. Have you got it working?
Thanks.

$COMPUTERNAME works for our Macs. I don't think this will work for iOS as it is only listed for MacOs.

What version of JSS are you using?
We don't use Casper for MDM. But $SERIALNUMBER should work for iOS.
Post an example of your Config profile. Lets have a look. Otherwise let your Jamf account manager know that the Admin Guide info is not working for you.

Here is my SCEP configuration profile for Macs ( I hope this helps! ):

URL
The base URL for the SCEP server
http://myscepserver.mydomain.com/certsrv/mscep/mscep.dll/

Subject
Representation of a X.500 name
CN=$COMPUTERNAME.mydomain.com

Subject Alternative Name Type
The type of a subject alternative name
DNS Name (selected)

Subject Alternative Name Value
The value of a subject alternative name
host/$COMPUTERNAME.mydomain.com

Challenge Type
Dynamic-Microsoft CA (selected)

URL to SCEP Admin
The URL of the page to use to retrieve the SCEP challenge
http://myscepserver.mydomain.com/certsrv/mscep_admin/

@Cem i am trying to add $EMAIL but it does not work. it only shows the same $EMAIL placeholder rether than the actual value.

jamf documentation suggests that the variables are still there... Are you using JAMF?

@Cem yeah i am using jamf Pro.

Perhaps reach out to Jamf support?

@Cem i will a create a ticket to jamf support. but i was just thinking if anyone else face the same issue.