ssb: Silence warning for unknown backplane revision

When using a BCM4318 in a PCMCIA format, I get a startup message that the
device uses backplane revision 0xF000000. Next a WARNING is logged. Despite
the message, the device works fine, This patch silences the warning.

Cc: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/ssb/main.c

@@ -1135,6 +1135,8 @@ static u32 ssb_tmslow_reject_bitmask(struct ssb_device *dev)
 	case SSB_IDLOW_SSBREV_25:     /* TODO - find the proper REJECT bit */
 	case SSB_IDLOW_SSBREV_27:     /* same here */
 		return SSB_TMSLOW_REJECT;	/* this is a guess */
+	case SSB_IDLOW_SSBREV:
+		break;
 	default:
 		WARN(1, KERN_INFO "ssb: Backplane Revision 0x%.8X\n", rev);
 	}