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>

arch/powerpc/oprofile/common.c

@@ -160,7 +160,7 @@ static int op_powerpc_create_files(struct dentry *root)
 		char buf[4];
 
 		snprintf(buf, sizeof buf, "%d", i);
-		dir = oprofilefs_mkdir(root->d_sb, root, buf);
+		dir = oprofilefs_mkdir(root, buf);
 
 		oprofilefs_create_ulong(root->d_sb, dir, "enabled", &ctr[i].enabled);
 		oprofilefs_create_ulong(root->d_sb, dir, "event", &ctr[i].event);