msm: kgsl: Read TTBR0 register correctly in all places

TTBR0 register can be 64 bit when CONFIG_IOMMU_LPAE is defined else
it is 32 bits. Fix the reading of this register to be 64 bit and 32
bit based on CONFIG_IOMMU_LPAE being defined.

Change-Id: Ib5d28959d5338255351b576a9e6ebb3e0b327d1a
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>