serial: msm_geni_serial: Do not start sequencer during port open

This change avoids running RX engine of UART when port open is in
progress and port configuration is taking place. This prevents
unnecessary stop rx operation also.

Change-Id: Ib9a51f66eb377aac867d44a1d5ebeec85df0b8c4
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>