xfs: don't allow negative error tags

Errors go from zero which means no error to XFS_ERRTAG_MAX (22).  My
static checker complains that xfs_errortag_add() puts an upper bound on
this but not a lower bound.  Let's fix it by making it unsigned.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_error.c

@@ -55,7 +55,7 @@ xfs_error_test(int error_tag, int *fsidp, char *expression,
 }
 
 int
-xfs_errortag_add(int error_tag, xfs_mount_t *mp)
+xfs_errortag_add(unsigned int error_tag, xfs_mount_t *mp)
 {
 	int i;
 	int len;

fs/xfs/xfs_error.h

@@ -128,7 +128,7 @@ extern int xfs_error_test(int, int *, char *, int, char *, unsigned long);
 	 xfs_error_test((tag), (mp)->m_fixedfsid, "expr", __LINE__, __FILE__, \
 			(rf))))
 
-extern int xfs_errortag_add(int error_tag, struct xfs_mount *mp);
+extern int xfs_errortag_add(unsigned int error_tag, struct xfs_mount *mp);
 extern int xfs_errortag_clearall(struct xfs_mount *mp, int loud);
 #else
 #define XFS_TEST_ERROR(expr, mp, tag, rf)	(expr)