serial: 8250: convert drivers to use up_to_u8250p()

up_to_u8250p() casts struct uart_port * to struct uart_8250_port *. Update code
to use it instead of open coded variant.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 2ffda79..e213da0 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1597,8 +1597,7 @@
 
 static void serial8250_disable_ms(struct uart_port *port)
 {
-	struct uart_8250_port *up =
-		container_of(port, struct uart_8250_port, port);
+	struct uart_8250_port *up = up_to_u8250p(port);
 
 	/* no MSR capabilities */
 	if (up->bugs & UART_BUG_NOMSR)
@@ -2801,8 +2800,7 @@
 {
 	struct uart_state *state = container_of(port, struct uart_state, port);
 	struct uart_port *uport = state->uart_port;
-	struct uart_8250_port *up =
-		container_of(uport, struct uart_8250_port, port);
+	struct uart_8250_port *up = up_to_u8250p(uport);
 
 	if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1)
 		return -EINVAL;
@@ -2838,8 +2836,7 @@
 {
 	struct uart_state *state = container_of(port, struct uart_state, port);
 	struct uart_port *uport = state->uart_port;
-	struct uart_8250_port *up =
-		container_of(uport, struct uart_8250_port, port);
+	struct uart_8250_port *up = up_to_u8250p(uport);
 	int rxtrig;
 
 	if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1 ||