net/wireless: ipw2200: Fix panic occurring in ipw_handle_promiscuous_tx()

The driver does not count space of radiotap fields when allocating skb for
radiotap packet. This leads to kernel panic with the following call trace:

...
[67607.676067] [<c152f90f>] error_code+0x67/0x6c
[67607.676067] [<c142f831>] ? skb_put+0x91/0xa0
[67607.676067] [<f8cf5e5b>] ? ipw_handle_promiscuous_tx+0x16b/0x2d0 [ipw2200]
[67607.676067] [<f8cf5e5b>] ipw_handle_promiscuous_tx+0x16b/0x2d0 [ipw2200]
[67607.676067] [<f8cf899b>] ipw_net_hard_start_xmit+0x8b/0x90 [ipw2200]
[67607.676067] [<f8741c5a>] libipw_xmit+0x55a/0x980 [libipw]
[67607.676067] [<c143d3e8>] dev_hard_start_xmit+0x218/0x4d0
...

This bug was found by VittGam.
https://bugzilla.kernel.org/show_bug.cgi?id=43255

Cc: stable@kernel.org
Signed-off-by: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ipw2x00/ipw2200.c

@@ -10472,7 +10472,7 @@ static void ipw_handle_promiscuous_tx(struct ipw_priv *priv,
 		} else
 			len = src->len;
 
-		dst = alloc_skb(len + sizeof(*rt_hdr), GFP_ATOMIC);
+		dst = alloc_skb(len + sizeof(*rt_hdr) + sizeof(u16)*2, GFP_ATOMIC);
 		if (!dst)
 			continue;