s5j/serial: add runtime PM support
s5j/serial: add runtime PM support

This commit adds runtime support calls to notify PM state machine when
UART activity is detected.

Change-Id: Ie549fbca6020b0b664dfb7a60a83e0fbbc6e5083
Signed-off-by: Heesub Shin <45471ea77bd08f3d26635f3f5adb40ba41250a2b@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT