arm64: mmu: dma remap fail with 1GB block mapping

The provision to map 1GB block, gives a problem during
dma_contiguous_remap when it attempts to remaps the dma
buffers into 4K. During this attempt to remap dma buffers
it overwrites pgd mapping for 1G bl ck, thus leaving an
unmapped hole.

Managing remapping of dma regions with 1G block mapping is
difficult hence avoid mapping 1G block and switch to
SECTION_SIZE mapping (2MB) when memory region overlaps
with dma buffers range.

Change-Id: I2aa4119b3aeb328a2b95cf22656d2ec36012716f
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>