cifs: missing directory in MAINTAINERS file

The include/uapi/linux/cifs directory (not just fs/cifs and
fs/smbfs_common) should be included in cifs entry in the
MAINTAINERS file.
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

MAINTAINERS

@@ -5145,6 +5145,7 @@ T:	git git://git.samba.org/sfrench/cifs-2.6.git
 F:	Documentation/admin-guide/cifs/
 F:	fs/cifs/
 F:	fs/smbfs_common/
+F:	include/uapi/linux/cifs
 
 COMPACTPCI HOTPLUG CORE
 M:	Scott Murray <scott@spiteful.org>