tty: serial: imx: move del_timer_sync() to avoid potential deadlock

del_timer_sync() acquires its own lock and doesn't have to be nested
within the spinlock of sport->port.lock in imx_set_termios(),  which
will cause potential deadlock.  Fix this by moving it outside.

Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Eric Miao <eric.miao@linaro.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/imx.c

@@ -932,6 +932,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 			ucr2 |= UCR2_PROE;
 	}
 
+	del_timer_sync(&sport->timer);
+
 	/*
 	 * Ask the core to calculate the divisor for us.
 	 */
@@ -962,8 +964,6 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 			sport->port.ignore_status_mask |= URXD_OVRRUN;
 	}
 
-	del_timer_sync(&sport->timer);
-
 	/*
 	 * Update the per-port timeout.
 	 */