ARM: rockchip: force built-in regulator support for PM

The rockchips suspend/resume code requires regulators to work,
and gives a compile-time error if they are not available:

arch/arm/mach-rockchip/built-in.o: In function `rk3288_suspend_finish':
:(.text+0x146): undefined reference to `regulator_suspend_finish'
arch/arm/mach-rockchip/built-in.o: In function `rk3288_suspend_prepare':
:(.text+0x18e): undefined reference to `regulator_suspend_prepare'

To solve this, we now enable regulators whenever they are needed,
which is what we do on a lot of other platforms as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-rockchip/Kconfig

@@ -11,6 +11,7 @@ config ARCH_ROCKCHIP
 	select HAVE_ARM_SCU if SMP
 	select HAVE_ARM_TWD if SMP
 	select DW_APB_TIMER_OF
+	select REGULATOR if PM
 	select ROCKCHIP_TIMER
 	select ARM_GLOBAL_TIMER
 	select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK