iommu/mediatek: Fix protect memory setting

In MediaTek's IOMMU design, When a iommu translation fault occurs
(HW can NOT translate the destination address to a valid physical
address), the IOMMU HW output the dirty data into a special memory
to avoid corrupting the main memory, this is called "protect memory".
the register(0x114) for protect memory is a little different between
mt8173 and mt2712.

In the mt8173, bit[30:6] in the register represents [31:7] of the
physical address. In the 4GB mode, the register bit[31] should be 1.
While in the mt2712, the bits don't shift. bit[31:7] in the register
represents [31:7] in the physical address, and bit[1:0] in the
register represents bit[33:32] of the physical address if it has.

Fixes: e6dec923 ("iommu/mediatek: Add mt2712 IOMMU support")
Reported-by: Honghui Zhang <honghui.zhang@mediatek.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>