xfs: fixed signedness of error code in xfs_inode_buf_verify

Prior to v3.17, XFS used positive error codes internally.  Commit
af8d9716 (xfs: inode recovery
readahead can race with inode buffer creation), upstream commit
b79f4a1c backported from later
releases need the error code signs reversed.  Negative error codes
will cause assertion failures (BUG_ON on kernels with assertions
enabled.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Brian Foster <bfoster@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

fs/xfs/xfs_inode_buf.c

@@ -99,7 +99,7 @@ xfs_inode_buf_verify(
 						XFS_RANDOM_ITOBP_INOTOBP))) {
 			if (readahead) {
 				bp->b_flags &= ~XBF_DONE;
-				xfs_buf_ioerror(bp, -EIO);
+				xfs_buf_ioerror(bp, EIO);
 				return;
 			}