iwl3945: remove double defined 3945 tfd structures

This patch removes doubly defined struct iwl3945_tfd_frame_data
and struct iwl3945_tfd_frame.

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