iwlwifi: legacy tx_cmd_protection function

Legacy (4965 and 3945) devices has different tx_cmd_protection routine.
Move to iwl-legacy.c

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
6 files changed