[ALSA] sound: rme32.c fix integer as NULL pointer warning

kernel style does assignment outside of if() statements.
sound/pci/rme32.c:1353:71: warning: Using plain integer as NULL pointer
Signed-off-by: NHarvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/rme32.c

@@ -1350,7 +1350,8 @@ static int __devinit snd_rme32_create(struct rme32 * rme32)
 		return err;
 	rme32->port = pci_resource_start(rme32->pci, 0);
 
-	if ((rme32->iobase = ioremap_nocache(rme32->port, RME32_IO_SIZE)) == 0) {
+	rme32->iobase = ioremap_nocache(rme32->port, RME32_IO_SIZE);
+	if (!rme32->iobase) {
 		snd_printk(KERN_ERR "unable to remap memory region 0x%lx-0x%lx\n",
 			   rme32->port, rme32->port + RME32_IO_SIZE - 1);
 		return -ENOMEM;