Update gen_autofdo_event.py and gcc-auto-profile.

Update gen_autofdo_event.py and gcc-auto-profile.

gen_autofdo_event.py was stumbling on models with stepping so
I updated the script to handle this case similar to the code in
https://github.com/andikleen/pmu-tools/blob/c6a5f63aede19def8886d6a8b74d7a55c38ca947/event_download.py

The second change was to tolerate cases when the CPU supports PEBS but the
perf command with /p fails. This can happen in, e.g., a virtual machine.

I regenerated gcc-auto-profile using the updated script.

contrib/ChangeLog:

	* gen_autofdo_event.py: handle stepping, non-working PEBS

gcc/ChangeLog:

	* config/i386/gcc-auto-profile: regenerate