block: Fix nr_vecs for inline integrity vectors

commit 087787959ce851d7bbb19f10f6e9241b7f85a3ca upstream.

Commit 9f060e22 changed the way we handle allocations for the
integrity vectors. When the vectors are inline there is no associated
slab and consequently bvec_nr_vecs() returns 0. Ensure that we check
against BIP_INLINE_VECS in that case.

Reported-by: David Milburn <dmilburn@redhat.com>
Tested-by: David Milburn <dmilburn@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>