um: Use generic irq Kconfig

No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jeff Dike <jdike@addtoit.com>

arch/um/Kconfig.common

@@ -3,14 +3,10 @@ config DEFCONFIG_LIST
 	option defconfig_list
 	default "arch/$ARCH/defconfig"
 
-# UML uses the generic IRQ subsystem
-config GENERIC_HARDIRQS
-	bool
-	default y
-
 config UML
 	bool
 	default y
+	select HAVE_GENERIC_HARDIRQS
 
 config MMU
 	bool