ANDROID: iommu/io-pgtable-arm: Free underlying page tables for large mappings

Consider the case where a 2N--where N > 1--MB buffer is composed
entirely of 4 KB pages. This means that at the second to last level,
the buffer will have N non-leaf entries that point to page tables
with 4 KB mappings.

When the buffer is unmapped, all N entries will be cleared at the
second to last level. However, the existing logic only checks if
it needs to free the underlying page tables for the first non-leaf
entry. Therefore, the page table memory for the other entries N-1
entries will be leaked.

Fix this memory leak by ensuring that we apply the same check to
all N entries that are being unmapped.

Bug: 178537788
Fixes: 4ad6f2a4 ("FROMLIST: iommu/io-pgtable-arm: Implement arm_lpae_unmap_pages()")
Change-Id: I44cb26296209d1e351b94c763a6b322809c1159a
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>