drm/msm: Use phys_addr_t for physical addresses

Use phys_addr_t to store physical addresses destined for iommu_map() to
support targets that can have more than 32 bits of physical address space.

Change-Id: Ic0dedbad8d87bf05c602bccdd48338086d76478d
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>