iwl3945: synchronize timestamp with uCode

In IBSS, TSF maintains local clock counters at each station. Network
Synchronization follows a completely distributed scheme where beacon frames
are generated. Each station maintain its own TSF timestamp, extracted from
beacon timestamps they recieved. Following patch synchronize this beacon timestamp
with uCode.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>