maru ARM board: clean up code

maru ARM board: clean up code

Remove MARU ARM board template from maru_board.c, it doesn't makes sense to take
an approach like this because x86 maru machine and arm maru machine are compiled for
different executables.
Drop leftovers of maru_board.c from maru_arm_board.c. Actually honour user-specified
RAM size for maru arm board, set bottom limit to 512 MB.

Do not initialize G3D MALI400 device in maru ARM SoC, we only need gles device from it
and we can initialize it explicitly.

Also bugs fixed:
- not registering ROM memory regions for migration during maru ARM SoC initialization;
- wrong chipid_and_omr array size;
- missleading initialization of ROM memory region alias.

Signed-off-by: Igor Mitsyanko <i.mitsyanko@samsung.com>