[XFS] Fix ABBA deadlock between i_mutex and iolock. Avoid calling

__blockdev_direct_IO for the DIO_OWN_LOCKING case for direct I/O reads
since it drops and reacquires the i_mutex while holding the iolock and
this violates the locking order.

SGI-PV: 955696
SGI-Modid: xfs-linux-melb:xfs-kern:26898a

Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: David Chatterton <chatz@sgi.com>