iwlagn: enable shadow register

For 6000 series devices and up, enable automatic update MAC's register
for better power usage in PSP mode

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-agn-lib.c b/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
index 019d4e7..ca3530c 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-lib.c
@@ -753,6 +753,12 @@
 	} else
 		iwlagn_txq_ctx_reset(priv);
 
+	if (priv->cfg->base_params->shadow_reg_enable) {
+		/* enable shadow regs in HW */
+		iwl_set_bit(priv, CSR_MAC_SHADOW_REG_CTRL,
+			0x800FFFFF);
+	}
+
 	set_bit(STATUS_INIT, &priv->status);
 
 	return 0;