dax: advance the iomap_iter on pte and pmd faults

Advance the iomap_iter on PTE and PMD faults. Each of these
operations assign a hardcoded size to iter.processed. Replace those
with an advance and status return.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://lore.kernel.org/r/20250224144757.237706-10-bfoster@redhat.com


Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>