iommu/iommu-debug: Make debug driver 32 bit compatible

Currently iommu-debug was enable only for 64 bit
targets as there were compilation issues coming
up while enabling it for 32 bit. Fix these issues
to ensure that we can use it on 32 bit targets
too.

Change-Id: If230af86f2fdd12fb5396f3b4736e57a123422bd
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>