iommu: msm: Add support for 64 bit GFAR register

msm_iommu_v1 supports both short and long descriptor
page tables. Hence GFAR should be 64-bit long with
LPAE mode. So, extend GFAR support for the same.

Change-Id: Iedfc11c948d3983058a33344ed8358676760b47c
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>