gpu: ion: Add more debug info to client debugfs IF

Add logging of buffer physical address (if allocation
is from physically contiguous heap) and iommu mapping
information to the ion client debug interface.

Change-Id: Id3a77c1b5e3c5d15b11b3612f07d10092922cdff
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>