mm: Remove "select SRCU"

Now that the SRCU Kconfig option is unconditionally selected, there is
no longer any point in selecting it.  Therefore, remove the "select SRCU"
Kconfig statements.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrew Morton
Cc: <linux-mm@kvack.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>

mm/Kconfig

@@ -667,7 +667,6 @@ config BOUNCE
 
 config MMU_NOTIFIER
 	bool
-	select SRCU
 	select INTERVAL_TREE
 
 config KSM