arm64: Update the ID_AA64MMFR0_EL1 fields

While here move to decimal for the _op and _CR definitions to be used
by a future macro to define the register when the assembler doesn't
know about it.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D40890

(cherry picked from commit b21402d058755f4b33a82fa8024fbf4501f5a218)