iwlagn: merge duplicated code into single place

Multiple places have similar code to construct calib header. Merge into
single inline function.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c b/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
index 23eee0c..ba7ed91 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
@@ -111,10 +111,8 @@
 
 		memset(&cmd, 0, sizeof(cmd));
 
-		cmd.hdr.op_code = priv->_agn.phy_calib_chain_noise_gain_cmd;
-		cmd.hdr.first_group = 0;
-		cmd.hdr.groups_num = 1;
-		cmd.hdr.data_valid = 1;
+		iwl_set_calib_hdr(&cmd.hdr,
+			priv->_agn.phy_calib_chain_noise_gain_cmd);
 		cmd.delta_gain_1 = data->delta_gain_code[1];
 		cmd.delta_gain_2 = data->delta_gain_code[2];
 		iwl_send_cmd_pdu_async(priv, REPLY_PHY_CALIBRATION_CMD,
@@ -144,10 +142,8 @@
 		data->beacon_count = 0;
 
 		memset(&cmd, 0, sizeof(cmd));
-		cmd.hdr.op_code = priv->_agn.phy_calib_chain_noise_reset_cmd;
-		cmd.hdr.first_group = 0;
-		cmd.hdr.groups_num = 1;
-		cmd.hdr.data_valid = 1;
+		iwl_set_calib_hdr(&cmd.hdr,
+			priv->_agn.phy_calib_chain_noise_reset_cmd);
 		ret = iwl_send_cmd_pdu(priv, REPLY_PHY_CALIBRATION_CMD,
 					sizeof(cmd), &cmd);
 		if (ret)