serial: msm_serial: add sparse context annotation

Add sparse context annotation to the receive handlers, which release and
reacquire the port lock, to silence sparse warnings:

	drivers/tty/serial/msm_serial.c:748:25: warning: context imbalance in 'msm_handle_rx_dm' - unexpected unlock
	drivers/tty/serial/msm_serial.c:814:28: warning: context imbalance in 'msm_handle_rx' - unexpected unlock
Signed-off-by: NJohan Hovold <johan@kernel.org>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200723123327.5843-3-johan@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/msm_serial.c

@@ -696,6 +696,7 @@ static void msm_enable_ms(struct uart_port *port)
 }
 
 static void msm_handle_rx_dm(struct uart_port *port, unsigned int misr)
+	__must_hold(&port->lock)
 {
 	struct tty_port *tport = &port->state->port;
 	unsigned int sr;
@@ -771,6 +772,7 @@ static void msm_handle_rx_dm(struct uart_port *port, unsigned int misr)
 }
 
 static void msm_handle_rx(struct uart_port *port)
+	__must_hold(&port->lock)
 {
 	struct tty_port *tport = &port->state->port;
 	unsigned int sr;