staging: sb105x: fix potential NULL pointer dereference in mp_chars_in_buffer()

The dereference to 'state' should be moved below the NULL test.

Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/sb105x/sb_pci_mp.c

@@ -689,13 +689,14 @@ static int mp_chars_in_buffer(struct tty_struct *tty)
 static void mp_flush_buffer(struct tty_struct *tty)
 {
 	struct sb_uart_state *state = tty->driver_data;
-	struct sb_uart_port *port = state->port;
+	struct sb_uart_port *port;
 	unsigned long flags;
 
 	if (!state || !state->info) {
 		return;
 	}
 
+	port = state->port;
 	spin_lock_irqsave(&port->lock, flags);
 	uart_circ_clear(&state->info->xmit);
 	spin_unlock_irqrestore(&port->lock, flags);