ARM: exynos: select PM_GENERIC_DOMAINS only when used

This fixes building exynos kernels with CONFIG_PM disabled.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/mach-exynos/Kconfig

@@ -38,7 +38,7 @@ config CPU_EXYNOS4210
 	depends on ARCH_EXYNOS4
 	select ARM_CPU_SUSPEND if PM
 	select PINCTRL_EXYNOS
-	select PM_GENERIC_DOMAINS
+	select PM_GENERIC_DOMAINS if PM
 	select S5P_PM if PM
 	select S5P_SLEEP if PM
 	select SAMSUNG_DMADEV