xfs: refactor xfs_verifier_error and xfs_buf_ioerror

xfs: refactor xfs_verifier_error and xfs_buf_ioerror

Source kernel commit: 31ca03c92c329525ee3a97d99c47f1ebbaed5d63

Since all verification errors also mark the buffer as having an error,
we can combine these two calls.  Later we'll add a xfs_failaddr_t
parameter to promote the idea of reporting corruption errors and the
address of the failing check to enable better debugging reports.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>