serial: msm_serial_hs: Do not accept Rx Data till the Rx pipe connect

In a resume path, sometimes RX is resetted and keep the RX BAM engine
enabled which actually makes RX to start accepting data when Flow
control is not disabled.

1. Keep the flow control disabled till the RX engine is fully enabled.
2. Use atomic variable to prevent race between startup and resume path.
3. Revert stop_rx changes, as we should not vote for the clock there.
4. Revert suspend time wakeup interrupt enable as clocks are ON and
   it can cause extra 0xFD injects in case of noise.

Change-Id: I5fe84b8d9f5118803e72974db3e6637c44b9c482
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>