arm64: Teach CHECK_CPU_FEAT to handle more values

CHECK_CPU_FEAT only supported checking for features that were enabled
when the field is non-zero. There are some features we might need to
check where we move between two non-zero values.

Support this by passing in the field value name to compare rather than
assuming a non-zero value.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D51375