Merge common ARM CPU/MMU code

This is to make sure all ARM platforms will benefit from planned work on this
MMU/CPU code. The less code duplicated, the better.

Compile-tested for all supported ARM platforms

Merge common ARM CPU/MMU code

This is to make sure all ARM platforms will benefit from planned work on this
MMU/CPU code. The less code duplicated, the better.

Compile-tested for all supported ARM platforms