iwlwifi: mvm: debugfs: add an option to set antennas for scan command

Add an option to set rx antennas for the scan command from debugfs.
Create a file called ant_rxchain in the mvm debugfs directory.
To choose antennas, write a number between 1-7 to ant_rxchain.
Write 1 for A, 2 for B, 3 for AB and so on.

Signed-off-by: Oren Givon <oren.givon@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/mvm/scan.c b/drivers/net/wireless/iwlwifi/mvm/scan.c
index 9a7ab84..71170fc 100644
--- a/drivers/net/wireless/iwlwifi/mvm/scan.c
+++ b/drivers/net/wireless/iwlwifi/mvm/scan.c
@@ -74,8 +74,12 @@
 static inline __le16 iwl_mvm_scan_rx_chain(struct iwl_mvm *mvm)
 {
 	u16 rx_chain;
-	u8 rx_ant = iwl_fw_valid_rx_ant(mvm->fw);
+	u8 rx_ant;
 
+	if (mvm->scan_rx_ant != ANT_NONE)
+		rx_ant = mvm->scan_rx_ant;
+	else
+		rx_ant = iwl_fw_valid_rx_ant(mvm->fw);
 	rx_chain = rx_ant << PHY_RX_CHAIN_VALID_POS;
 	rx_chain |= rx_ant << PHY_RX_CHAIN_FORCE_MIMO_SEL_POS;
 	rx_chain |= rx_ant << PHY_RX_CHAIN_FORCE_SEL_POS;