Don't add suffix if user added it already

[jtagcat]

$ ssh-tpm-keygen
Generating a sealed public/private ecdsa key pair.
Enter file in which to save the key (/home/jc/.ssh/id_ecdsa): /home/jc/.ssh/hh-8192_ecdsa.tpm
Enter pin (empty for no pin):
Confirm pin:
Your identification has been saved in /home/jc/.ssh/hh-8192_ecdsa.tpm.tpm

Expected. Your identification has been saved in /home/jc/.ssh/hh-8192_ecdsa.tpm

[sagar2395]

@jtagcat i would like to work on this issue