ANDROID: iommu/arm-smmu-v3-kvm: Don't rely on post_table_walk

There is a problem at the moment that a map operation can trigger
an unmap when a table is replaced with a block, that means that the
count for those is leaked, to fix this we need to find a way of decrementing
the refcount from map context.

Instead of adding complexity to pass a walker to map, we can rely on
the existing callback tlb_flush_walk which is called per freed table.
This also simplfies unmap, as we can untrack tables from that call
and not rely on the post table walk.

In this patch we remove the post table walk, and assume that the table
is freed from the core, and in the next patch we revert the changes
that add the post table walker and make the table freed with
IO_PGTABLE_QUIRK_UNMAP_INVAL.

Bug: 357781595
Bug: 384432312
Change-Id: I983d1ff903fb0c71a54025fcb34b9b0004613b29
Signed-off-by: Mostafa Saleh <smostafa@google.com>