refactor(mediatek): move headers to common folder

The plat_macros.S and plat_private.h are identical across some
platforms, moved to the common folder for easier maintenance.

Change-Id: I31c71551aa0e891f080e58f21e6e79551d2a19e0
Signed-off-by: Gavin Liu <gavin.liu@mediatek.com>
15 files changed