msm: kgsl: Report cff dump virtual address range correctly

When IOMMU is used then the vitual address can range from the base
address used when per process pagetable is disabled upto the last
address that can be assigned to a kgsl allocated memory region.
Report this range correctly in CFF.

Change-Id: Ib1798434b60f1e3cd4c0570456bf4b075ffa2afd
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>