feat(mediatek): introduce mtk init framework

feat(mediatek): introduce mtk init framework

Provide six initcall levels for drivers/modules initialize HW
controllers or runtime arguments during cold boot.

The initcall level cold boot execution order:

-MTK_EARLY_PLAT_INIT
Call before MMU enabled.

-MTK_ARCH_INIT
MMU Enabled, arch related init(GiC init, interrupt type registration).

-MTK_PLAT_SETUP_0_INIT
MTK driver init level 0.

-MTK_PLAT_SETUP_1_INIT
MTK driver init level 1.

-MTK_PLAT_RUNTIME_INIT
MTK driver init. After this initcall, TF-A handovers to MTK 2nd
bootloader.

-MTK_PLAT_BL33_DEFER_INIT
MTK 2nd bootloader traps to TF-A before handover to rich OS.
This initcall executed in the trap handler(boot_to_kernel).

Signed-off-by: Leon Chen <leon.chen@mediatek.com>
Change-Id: Icd7fe95372441db73c975ccb6ce77a6c529df1cc