wifi: rtw88: Use random MAC when efuse MAC invalid

When the MAC address read from the efuse data is invalid, warn the
user and use a random MAC address instead.

On a device I am currently using (Anbernic RG-ARC) with a rtw8821cs
the efuse appears to be incompletely/improperly programmed. The MAC
address reads as ff:ff:ff:ff:ff:ff. When networkmanager attempts to
initiate a connection (and I haven't hard-coded a MAC address or
set it to random) it fails to establish a connection.
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231208150739.129753-1-macroalpha82@gmail.com

drivers/net/wireless/realtek/rtw88/main.c

@@ -2008,6 +2008,11 @@ static int rtw_chip_efuse_info_setup(struct rtw_dev *rtwdev)
 	efuse->ext_pa_5g = efuse->pa_type_5g & BIT(0) ? 1 : 0;
 	efuse->ext_lna_2g = efuse->lna_type_5g & BIT(3) ? 1 : 0;
 
+	if (!is_valid_ether_addr(efuse->addr)) {
+		eth_random_addr(efuse->addr);
+		dev_warn(rtwdev->dev, "efuse MAC invalid, using random\n");
+	}
+
 out_disable:
 	rtw_chip_efuse_disable(rtwdev);