iwlagn: remove duplicate list init

iwl_trans_rx_alloc is only called from iwl_rx_init, so no need
to init the lists twice.

Signed-off-by: Amit Beka <amit.beka@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>