iwlagn: remove legacy calibration command

IWL_PHY_CALIBRATE_DIFF_GAIN_CMD is for legacy device, remove it
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

drivers/net/wireless/iwlwifi/iwl-commands.h

@@ -3155,7 +3155,6 @@ struct iwl_enhance_sensitivity_cmd {
 /* The default calibrate table size if not specified by firmware */
 #define IWL_DEFAULT_STANDARD_PHY_CALIBRATE_TBL_SIZE	18
 enum {
-	IWL_PHY_CALIBRATE_DIFF_GAIN_CMD		= 7,
 	IWL_PHY_CALIBRATE_DC_CMD		= 8,
 	IWL_PHY_CALIBRATE_LO_CMD		= 9,
 	IWL_PHY_CALIBRATE_TX_IQ_CMD		= 11,
@@ -3221,15 +3220,6 @@ struct iwl_calib_cmd {
 	u8 data[0];
 } __packed;
 
-/* IWL_PHY_CALIBRATE_DIFF_GAIN_CMD (7) */
-struct iwl_calib_diff_gain_cmd {
-	struct iwl_calib_hdr hdr;
-	s8 diff_gain_a;		/* see above */
-	s8 diff_gain_b;
-	s8 diff_gain_c;
-	u8 reserved1;
-} __packed;
-
 struct iwl_calib_xtal_freq_cmd {
 	struct iwl_calib_hdr hdr;
 	u8 cap_pin1;