iwlwifi: don't disable SCD chain extension on newer devices

7000 device series have a fix for this hardware feature.
Stop disabling it, and get an improvement in Tx throughput.
This feature allows the scheduler to fetch more frames on
the fly while an A-MPDU is being built - which means that
we can get larger A-MPDU. This, of course, give an
improvement in the Tx throughput.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

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

@@ -148,6 +148,7 @@ static inline u8 num_of_ant(u8 mask)
  * @shadow_reg_enable: HW shadow register support
  * @apmg_wake_up_wa: should the MAC access REQ be asserted when a command
  *	is in flight. This is due to a HW bug in 7260, 3160 and 7265.
+ * @scd_chain_ext_wa: should the chain extension feature in SCD be disabled.
  */
 struct iwl_base_params {
 	int eeprom_size;
@@ -163,6 +164,7 @@ struct iwl_base_params {
 	const bool shadow_reg_enable;
 	const bool pcie_l1_allowed;
 	const bool apmg_wake_up_wa;
+	const bool scd_chain_ext_wa;
 };
 
 /*