[ARM] arm32: Add support for ARMv6 processors

This extends arm32 CPU support for ARMv6 processors.

The ARMv7 MMU is fully backward compatible to ARMv6 MMU.

Also, ARMv6 instruction-set is sub-set of ARMv7 instruction-set. In fact, ARMv7 has only few additional instructions.

Signed-off-by: Anup Patel <anup@brainfault.org>