[ARM] Moved MMU code for LPAE into arm/cpu/common/

MMU code for LPAE can be shared between arm32ve and arm64 so we move it
into arch/arm/cpu/common/

Signed-off-by: Sukanto Ghosh <sukantoghosh@gmail.com>
Signed-off-by: Anup Patel <anup@brainfault.org>