sysv: drop lock/unlock super

Removed lock/unlock super. Added a new private s_lock mutex.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/sysv/sysv.h b/fs/sysv/sysv.h
index 0bc35fd..69d4889 100644
--- a/fs/sysv/sysv.h
+++ b/fs/sysv/sysv.h
@@ -58,6 +58,7 @@
 	u32            s_nzones;	/* same as s_sbd->s_fsize */
 	u16	       s_namelen;       /* max length of dir entry */
 	int	       s_forced_ro;
+	struct mutex s_lock;
 };
 
 /*