b43: remove rate index warning

I frequently run into this warning, and added some
debugging to see why, and got this:

b43 bad rx: 00000000: 2f d2 e2 63 cf a7 14 04 28 18 c8 5f 88 4a a2 00
                      bogus junk       | plcp            | fctl| dur

b43 bad rx: 00000010: 00 11 24 91 07 4d 00 06 25 ff 8f 78 00 06 25 ff
                      my MAC address   | BSSID           | AP MAC
b43 bad rx: 00000020: 8f 76 20 74 00 00 42 07 00 20 00 00 00 00 aa aa
                           | seq | QoS | CCMP IV               | data
                      ...

As you can see, there are 6 bogus bytes (sometimes only five) and then
the frame. I don't know why, and I don't see how to recover, so let's
just drop these frames.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/xmit.c

@@ -46,7 +46,6 @@ static int b43_plcp_get_bitrate_idx_cck(struct b43_plcp_hdr6 *plcp)
 	case 0x6E:
 		return 3;
 	}
-	B43_WARN_ON(1);
 	return -1;
 }
 
@@ -73,7 +72,6 @@ static u8 b43_plcp_get_bitrate_idx_ofdm(struct b43_plcp_hdr6 *plcp, bool aphy)
 	case 0xC:
 		return base + 7;
 	}
-	B43_WARN_ON(1);
 	return -1;
 }
 
@@ -608,6 +606,8 @@ void b43_rx(struct b43_wldev *dev, struct sk_buff *skb, const void *_rxhdr)
 						phytype == B43_PHYTYPE_A);
 	else
 		status.rate_idx = b43_plcp_get_bitrate_idx_cck(plcp);
+	if (unlikely(status.rate_idx == -1))
+		goto drop;
 	status.antenna = !!(phystat0 & B43_RX_PHYST0_ANT);
 
 	/*