Refresh CPU types and classes from sys/sys/pmc.h.

While here, fix a few nits.

Inspired by reviewing D35342.

Sources for trademark info

• https://www.arm.com/company/policies/trademarks (no Arm8, curiously)
• https://www.ibm.com/legal/copytrade?mhsrc=ibmsearch_a&mhq=trademark

Reviewed by: carlavilla, luporl, mhorne
Approved by: carlavilla (mentor), mhorne (src)
Differential Revision: https://reviews.freebsd.org/D35344