iommu/mediatek: Refine protect memory definition

The protect memory setting is a little different in the different SoCs.
In the register REG_MMU_CTRL_REG(0x110), the TF_PROT(translation fault
protect) shift bit is normally 4 while it shift 5 bits only in the
mt8173. This patch delete the complex MACRO and use a common if-else
instead.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Evan Green <evgreen@chromium.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>