xfs: remove deprecated barrier/nobarrier mount

The barrier mount options have been no-ops and deprecated since

4cf4573 xfs: deprecate barrier/nobarrier mount option

i.e. kernel 4.10 / December 2016, with a stated deprecation schedule
after v4.15.  Should be fair game to remove them now.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Documentation/filesystems/xfs.txt

@@ -223,8 +223,6 @@ Deprecated Mount Options
 
   Name				Removal Schedule
   ----				----------------
-  barrier			no earlier than v4.15
-  nobarrier			no earlier than v4.15
 
 
 Removed Mount Options
@@ -236,6 +234,8 @@ Removed Mount Options
   ihashsize			v4.0
   irixsgid			v4.0
   osyncisdsync/osyncisosync	v4.0
+  barrier			v4.19
+  nobarrier			v4.19
 
 
 sysctls