ARM: SAMSUNG: Add SAMSUNG_PM config option to select pm

ARM: SAMSUNG: Add SAMSUNG_PM config option to select pm

This patch enables the selection of samsung pm related stuffs
when SAMSUNG_PM config is enabled and not just when generic PM
config is enabled. Power management for s3c64XX and s3c24XX
is enabled by default and for other platform depends on S5P_PM.
This patch also fixes the following compilation error's when compiling
a platform like exynos5440 which does not select pm stuffs.

arch/arm/mach-exynos/built-in.o: In function '__virt_to_phys':
linux/arch/arm/include/asm/memory.h:175: undefined reference to 's3c_cpu_resume'
linux/arch/arm/include/asm/memory.h:175: undefined reference to 's3c_cpu_resume'
linux/arch/arm/include/asm/memory.h:175: undefined reference to 's3c_cpu_resume'
linux/arch/arm/include/asm/memory.h:175: undefined reference to 's3c_cpu_resume'
arch/arm/mach-exynos/built-in.o: In function 'exynos5_init_irq':
linux/arch/arm/mach-exynos/common.c:492: undefined reference to 's3c_irq_wake'
linux/arch/arm/mach-exynos/common.c:492: undefined reference to 's3c_irq_wake'
arch/arm/mach-exynos/built-in.o: In function 'exynos4_init_irq':
linux/arch/arm/mach-exynos/common.c:476: undefined reference to 's3c_irq_wake'
linux/arch/arm/mach-exynos/common.c:476: undefined reference to 's3c_irq_wake'
arch/arm/plat-samsung/built-in.o: In function 's3c_irqext_wake':
linux/arch/arm/plat-samsung/pm.c:144: undefined reference to 's3c_irqwake_eintallow'
linux/arch/arm/plat-samsung/pm.c:144: undefined reference to 's3c_irqwake_eintallow'
arch/arm/plat-samsung/built-in.o: In function 's3c_pm_enter':
linux/arch/arm/plat-samsung/pm.c:263: undefined reference to 's3c_irqwake_intallow'
linux/arch/arm/plat-samsung/pm.c:263: undefined reference to 's3c_irqwake_intallow'
linux/arch/arm/plat-samsung/pm.c:264: undefined reference to 's3c_irqwake_eintallow'
linux/arch/arm/plat-samsung/pm.c:264: undefined reference to 's3c_irqwake_eintallow'
linux/arch/arm/plat-samsung/pm.c:275: undefined reference to 's3c_pm_save_core'
linux/arch/arm/plat-samsung/pm.c:279: undefined reference to 's3c_pm_configure_extint'
linux/arch/arm/plat-samsung/pm.c:310: undefined reference to 's3c_pm_restore_core'
make: *** [vmlinux] Error 1

Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>