MLK-10274 tty: serial: clear AWAKE bit after resume back

When uart port (non-console port) in dma mode and use uart as remote wakeup
source, after resume back, the AWAKE bit is not cleared most of interrupts
are disabled. And then let system suspend state, system resume back immediately
without any wake up action. So we need to clear the AWAKE bit after resume
back in DMA mode.

Signed-off-by: Fugang Duan <B38611@freescale.com>
(cherry picked from commit: c0a665e33dd69276a2142933354e18d4f3b20453)