display proper message with proper errno for kvm.

[hdwhdw]

What I did

In KVM, there is no system EEPROM. decode-syseeprom should display the information and return the correct errno (ENODEV).

Currently, on KVM, decode-syseeprom will return OK (0) even if there is no system EEPROM.

How I did it

Check if the platform is kvm, if so, log and return.

How to verify it

root@vlab-01:~# decode-syseeprom
Platform x86_64-kvm_x86_64-r0 does not support EEPROM
root@vlab-01:~# echo $?
19
root@vlab-01:~# python3 -c 'import os, sys; print(os.strerror(int(sys.argv[1])))' 19
No such device

Previous command output (if the output of a command-line utility has changed)

admin@vlab-01:~$ sudo decode-syseeprom -s
Failed to read system EEPROM info
admin@vlab-01:~$ echo $?
0

New command output (if the output of a command-line utility has changed)

[mssonicbld]

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