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>
diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.c b/drivers/net/wireless/iwlwifi/iwl-4965.c
index a6518ca..cd14843 100644
--- a/drivers/net/wireless/iwlwifi/iwl-4965.c
+++ b/drivers/net/wireless/iwlwifi/iwl-4965.c
@@ -2514,7 +2514,7 @@
 	.build_addsta_hcmd = iwl4965_build_addsta_hcmd,
 	.chain_noise_reset = iwl4965_chain_noise_reset,
 	.gain_computation = iwl4965_gain_computation,
-	.tx_cmd_protection = iwlcore_tx_cmd_protection,
+	.tx_cmd_protection = iwl_legacy_tx_cmd_protection,
 	.calc_rssi = iwl4965_calc_rssi,
 	.request_scan = iwlagn_request_scan,
 	.post_scan = iwl4965_post_scan,