serial: 68328serial: Use NULL for pointers

Compare pointer-typed values to NULL rather than 0

The semantic patch that makes this change is available
in scripts/coccinelle/null/badzero.cocci.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/68328serial.c

@@ -560,8 +560,8 @@ static void rs_fair_output(void)
 	struct m68k_serial *info = &m68k_soft[0];
 	char c;
 
-	if (info == 0) return;
-	if (info->xmit_buf == 0) return;
+	if (info == NULL) return;
+	if (info->xmit_buf == NULL) return;
 
 	local_irq_save(flags);
 	left = info->xmit_cnt;