[PATCH] ipw2200: remove the MAC timestamp present field from radiotap head

IEEE80211_RADIOTAP_TSFT is defined as the Value in microseconds of the
MAC's 64-bit 802.11 Time Synchronization Function timer when the first bit
of the MPDU arrived at the MAC. Since ipw2200 hardware doesn't provide this
value, we disable this feature from the radiotap header present flag.

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