mm: Update validate_mm() to use vma iterator

mm: Update validate_mm() to use vma iterator

Use the vma iterator in the validation code and combine the code to
check the maple tree into the main validate_mm() function.

Introduce a new function vma_iter_dump_tree() to dump the maple tree in
hex layout.

Replace all calls to validate_mm_mt() with validate_mm().

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>