serial: core: lock port for start_rx() in uart_resume_port()

The only user of the start_rx() callback (qcom_geni) directly calls
its own stop_rx() callback. Since stop_rx() requires that the
port->lock is taken and interrupts are disabled, the start_rx()
callback has the same requirement.

Fixes: cfab87c2 ("serial: core: Introduce callback for start_rx and do stop_rx in suspend only if this callback implementation is present.")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230525093159.223817-5-john.ogness@linutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>