oprofilefs_mkdir() doesn't need superblock argument

it's always equal to ->d_sb of the second argument (parent dentry),
due to either being literally that, or ->d_sb of parent's parent.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/oprofile.h b/include/linux/oprofile.h
index 8a906b4..957877e 100644
--- a/include/linux/oprofile.h
+++ b/include/linux/oprofile.h
@@ -144,8 +144,7 @@
 	char const * name, atomic_t * val);
  
 /** create a directory */
-struct dentry * oprofilefs_mkdir(struct super_block * sb, struct dentry * root,
-	char const * name);
+struct dentry *oprofilefs_mkdir(struct dentry *parent, char const *name);
 
 /**
  * Write the given asciz string to the given user buffer @buf, updating *offset