drm/msm: Use dma_addr_t to manage iova

GPU address could be 64-bits, Use dma_addr_t instead of
uint_32_t to avoid truncation issue.

Change-Id: I1ac6bbff31ce8f95afd7e2f9accc4823e8b49565
Signed-off-by: Kasin Li <donglil@codeaurora.org>
Signed-off-by: Yajun Li <yajunl@codeaurora.org>