mm/mlock: Use maple state in apply_mlockall_flags()

mm/mlock:  Use maple state in apply_mlockall_flags()

The vma iterator is for simple cases.  Since mlock_fixup() can cause the
tree to change and thus requires the maple state to be reset,
apply_mlockall_flags() is not a simple case.  Use a maple state and
call mas_pause() instead.

Fixes: 0d43186b36c1 (mm/mlock: use vma iterator and instead of vma
linked list)
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>