TTY: serial: move the dereference below the NULL test

The dereference should be moved below the NULL test.

spatch with a semantic match is used to found this.
(http://coccinelle.lip6.fr/)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/ioc3_serial.c

@@ -1120,13 +1120,14 @@ static inline int do_read(struct uart_port *the_port, char *buf, int len)
 	struct ioc3_port *port = get_ioc3_port(the_port);
 	struct ring *inring;
 	struct ring_entry *entry;
-	struct port_hooks *hooks = port->ip_hooks;
+	struct port_hooks *hooks;
 	int byte_num;
 	char *sc;
 	int loop_counter;
 
 	BUG_ON(!(len >= 0));
 	BUG_ON(!port);
+	hooks = port->ip_hooks;
 
 	/* There is a nasty timing issue in the IOC3. When the rx_timer
 	 * expires or the rx_high condition arises, we take an interrupt.

drivers/tty/serial/ioc4_serial.c

@@ -2069,13 +2069,14 @@ static inline int do_read(struct uart_port *the_port, unsigned char *buf,
 	struct ioc4_port *port = get_ioc4_port(the_port, 0);
 	struct ring *inring;
 	struct ring_entry *entry;
-	struct hooks *hooks = port->ip_hooks;
+	struct hooks *hooks;
 	int byte_num;
 	char *sc;
 	int loop_counter;
 
 	BUG_ON(!(len >= 0));
 	BUG_ON(!port);
+	hooks = port->ip_hooks;
 
 	/* There is a nasty timing issue in the IOC4. When the rx_timer
 	 * expires or the rx_high condition arises, we take an interrupt.