xfs/656: rearrange directio pread/pwrite for zoned filesystems

On zoned filesystems, a write failure shuts down the filesystem, which
makes this test fail with:

 --- /run/fstests/bin/tests/xfs/656.out	2026-03-13 16:19:08.152939212 -0700
 +++ /run/fstests/logs/xfs/656.out.bad	2026-06-30 18:16:43.847849604 -0700
 @@ -1,10 +1,9 @@
  QA output created by 656
  Format and mount
  pwrite: Input/output error
 -pread: Input/output error
 +stat: Input/output error
  pread: Input/output error
  fsync: Input/output error
  VICTIM pos NUM len NUM: directio_write: Input/output error
 -VICTIM pos NUM len NUM: directio_read: Input/output error
  VICTIM pos NUM len NUM: buffered_read: Input/output error
  VICTIM pos NUM len NUM: buffered_write: Input/output error

Reorder the directio pread and pwrite to avoid this unnecessary failure.
Note that we cycle the mount between the direct and buffered io tests,
which is why we only need to fix the directio test.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Zorro Lang <zlang@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>