mt76: mt7615: report firmware version using ethtool

Print fw_ver and build_date members of struct mt7615_fw_trailer
similarly to what appears in the output of 'dmesg' when the MCU firmware
is loaded.
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/mcu.c

@@ -514,8 +514,14 @@ static int mt7615_load_ram(struct mt7615_dev *dev)
 		goto out;
 
 	ret = mt7615_mcu_start_firmware(dev, 0, FW_START_WORKING_PDA_CR4);
-	if (ret)
+	if (ret) {
 		dev_err(dev->mt76.dev, "Failed to start CR4 firmware\n");
+		goto out;
+	}
+
+	snprintf(dev->mt76.hw->wiphy->fw_version,
+		 sizeof(dev->mt76.hw->wiphy->fw_version),
+		 "%.10s-%.15s", hdr->fw_ver, hdr->build_date);
 
 out:
 	release_firmware(fw);