iwl3945: iwl3945_queue and iwl3945_channel_info replacement

This patch replaces the queue and channel info 3945 structures with the iwl
ones.

The initial goal was to replace the channel info structure. Once we do that,
and then include iwl-dev.h instead of iwl-3945.h, we still get build errors
due to several routines and macro redefinitions. This is why this patch also
includes:
- TFD39_MAX_PAYLOAD definition for 3945.
- CMD_SIZE, CMD_HUGE, CMD_SKB duplication removal.
- iwl3945_queue replacement in order to also get rid of the duplicated
get_cmd_index routine.

Getting rid of any of those needs the iwl-dev.h inclusion which then creates
build errors due to definitions duplication. This is why we include all those
in the same patch.

Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
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>