xfs: turn the XFS_DA_OP_REPLACE checks in xfs_attr_shortform_addname into asserts

Since commit deed9512 ("xfs: Check for -ENOATTR or -EEXIST"), the
high-level attr code does a lookup for any attr we're trying to set,
and does the checks to handle the create vs replace cases, which thus
never hit the low-level attr code.

Turn the checks in xfs_attr_shortform_addname as they must never trip.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

fs/xfs/libxfs/xfs_attr.c

@@ -1072,8 +1072,7 @@ xfs_attr_shortform_addname(
 	if (xfs_attr_sf_findname(args)) {
 		int		error;
 
-		if (!(args->op_flags & XFS_DA_OP_REPLACE))
-			return -EEXIST;
+		ASSERT(args->op_flags & XFS_DA_OP_REPLACE);
 
 		error = xfs_attr_sf_removename(args);
 		if (error)
@@ -1087,8 +1086,7 @@ xfs_attr_shortform_addname(
 		 */
 		args->op_flags &= ~XFS_DA_OP_REPLACE;
 	} else {
-		if (args->op_flags & XFS_DA_OP_REPLACE)
-			return -ENOATTR;
+		ASSERT(!(args->op_flags & XFS_DA_OP_REPLACE));
 	}
 
 	if (args->namelen >= XFS_ATTR_SF_ENTSIZE_MAX ||