ARM: TWD: enable one-shot mode

Allow one shot timer mode to be used with the TWD.  This allows
NOHZ mode to be used on SMP systems using the TWD localtimer.

Tested on Versatile Express and U8500.
Tested-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -1248,6 +1248,7 @@ config HAVE_ARM_SCU
 config HAVE_ARM_TWD
 	bool
 	depends on SMP
+	select TICK_ONESHOT
 	help
 	  This options enables support for the ARM timer and watchdog unit