msm: wfd: Revert back to using 32 bit physical addresses

This commit partially reverts the move to 64 bit physical addresses
by the use of dma_addr_t.  On targets that have LPAE enabled,
map_iommu() returns a 64 type despite only 32 bits of it being used.
It's somewhat difficult to pass around these 64 bit type, due the v4l2
spec only accepting 32 bit addresses.  Hence, as soon as each subdev
get a physical address, immediately drop the top 32 bits.

Change-Id: Icd5d684141f081a749c2f28274aeefea5d33e7c9
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>