ARM: S3C64XX: Reduce residency requirement for cpuidle WFI mode

Entering and leaving WFI is really cheap so there's no reason to have much
of a residency requirement for the state. Lower it to 1ms.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>