[PATCH] ipw2100: Fix dropping fragmented small packet problem

The rx_data.header struct is ieee80211_hdr_4addr. If a wireless frame uses
ieee80211_hdr_3addr header and is less than 6 bytes, it will be discarded.
This is not likely going to happen for normal packets (since there is TCP, IP
headers). But if fragmentation is used, there will be such small trailing
packets. And they will be lost for ever.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>