iommu: msm: always use 32-bit physical addresses

TZ expects the physical address of the destination dump buffer to be
32-bits, even on LPAE targets. Always send a 32-bit integer. This
requires truncating the top 4 bytes of a 64-bit physical address, but
this shouldn't be a problem on current targets since all physical
addresses should be <4GB.

Change-Id: I486ed39e132be46ebfc80335024cb8d31d7ac1c2
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>