iommu: iommu-debug: Add support for page table dump

Add support for page table dump for test domain.

eg:
cd /d/iommu/tests/soc:apps_iommu_test_device
echo 1 > attach
echo 0x20000,0x80000000,0x10000,0x1 > map
echo 0x21000,0x1000 > unmap
echo 0x24000,0x1000 > unmap
cat iommu_page_tables

---[ start ]---
0x0000000000020000-0x0000000000021000 4K PTE USR ro x AF NG DEVICE/nGnRnE
0x0000000000022000-0x0000000000024000 8K PTE USR ro x AF NG DEVICE/nGnRnE
0x0000000000025000-0x0000000000030000 44K PTE USR ro x AF NG DEVICE/nGnRnE

Change-Id: I56ac2615c4aa30dd75a2cdc1cf46de042e681cdc
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>