oprofile: get rid of pointless forward declarations of struct super_block

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/oprofile/oprofile_stats.h

@@ -25,7 +25,6 @@ extern struct oprofile_stat_struct oprofile_stats;
 /* reset all stats to zero */
 void oprofile_reset_stats(void);
 
-struct super_block;
 struct dentry;
 
 /* create the stats/ dir */