ARM: S3C64XX: fix building without CONFIG_PM_SLEEP

arch/arm/mach-s3c64xx/built-in.o: In function `s3c_pm_restore_core':
:(.text+0x5d0): undefined reference to `s3c_pm_do_restore_core'
:(.text+0x5d4): undefined reference to `s3c_pm_do_restore'
arch/arm/mach-s3c64xx/built-in.o: In function `s3c_pm_save_core':
:(.text+0x60c): undefined reference to `s3c_pm_do_save'
arch/arm/mach-s3c64xx/built-in.o: In function `s3c64xx_irq_pm_resume':
:(.text+0x670): undefined reference to `s3c_pm_do_restore'
arch/arm/mach-s3c64xx/built-in.o: In function `s3c64xx_irq_pm_suspend':
:(.text+0x6d8): undefined reference to `s3c_pm_do_save'
arch/arm/mach-s3c64xx/built-in.o: In function `s3c_cpu_resume':
:(.text+0x71c): undefined reference to `cpu_resume'

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kukjin Kim <kgene@kernel.org>