tty: use container_of to resolve uart_pmac_port from uart_port

Use container_of instead of casting first structure member.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pmac_zilog.c

@@ -1352,7 +1352,8 @@ static int pmz_verify_port(struct uart_port *port, struct serial_struct *ser)
 
 static int pmz_poll_get_char(struct uart_port *port)
 {
-	struct uart_pmac_port *uap = (struct uart_pmac_port *)port;
+	struct uart_pmac_port *uap =
+		container_of(port, struct uart_pmac_port, port);
 	int tries = 2;
 
 	while (tries) {
@@ -1367,7 +1368,8 @@ static int pmz_poll_get_char(struct uart_port *port)
 
 static void pmz_poll_put_char(struct uart_port *port, unsigned char c)
 {
-	struct uart_pmac_port *uap = (struct uart_pmac_port *)port;
+	struct uart_pmac_port *uap =
+		container_of(port, struct uart_pmac_port, port);
 
 	/* Wait for the transmit buffer to empty. */
 	while ((read_zsreg(uap, R0) & Tx_BUF_EMP) == 0)
@@ -1954,7 +1956,8 @@ static void __exit exit_pmz(void)
 
 static void pmz_console_putchar(struct uart_port *port, int ch)
 {
-	struct uart_pmac_port *uap = (struct uart_pmac_port *)port;
+	struct uart_pmac_port *uap =
+		container_of(port, struct uart_pmac_port, port);
 
 	/* Wait for the transmit buffer to empty. */
 	while ((read_zsreg(uap, R0) & Tx_BUF_EMP) == 0)