[SCSI] mac_scsi: Fix crash on out of memory

Missing check on scsi_register
Signed-off-by: NAlan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

drivers/scsi/mac_scsi.c

@@ -260,6 +260,8 @@ int __init macscsi_detect(struct scsi_host_template * tpnt)
     /* Once we support multiple 5380s (e.g. DuoDock) we'll do
        something different here */
     instance = scsi_register (tpnt, sizeof(struct NCR5380_hostdata));
+    if (instance == NULL)
+	return 0;
 
     if (macintosh_config->ident == MAC_MODEL_IIFX) {
 	mac_scsi_regp  = via1+0x8000;