serial: st-asc: Potential error pointer dereference

It looks like we intended to return an error code here, because we
dereference "ascport->pinctrl" on the next lines.

Fixes: 6929cb00 ("serial: st-asc: Read in all Pinctrl states")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/st-asc.c

@@ -758,6 +758,7 @@ static int asc_init_port(struct asc_port *ascport,
 	if (IS_ERR(ascport->pinctrl)) {
 		ret = PTR_ERR(ascport->pinctrl);
 		dev_err(&pdev->dev, "Failed to get Pinctrl: %d\n", ret);
+		return ret;
 	}
 
 	ascport->states[DEFAULT] =