cpu: New cpu_get_pcpuid(), retrieves internal CPU ID

[olce]

Summary

It is a handy shortcut that will be used extensively in
hwpstate_intel(4) and hwpstate_amd(4).

[jhb]

sys/sys/cpu.h

45

This can now use __BUS_ACCESSOR_DEFAULT() to return NULL by default, which will also mean you can start using cpu_has_pcpu in the pstate drivers to check for the ivar being valid vs manually calling BUS_READ_IVAR. It wouldn't be a functional change, just a cosmetic change that spells things more typically. (Unrelated to this commit, just a nice cleanup you can do as a separate commit)

65

This can also now use __BUS_ACCESSOR_DEFAULT() with a default value of -1.

[olce]

Thanks, will do some followup next week.