a10_gpio previously accepted only {allwinner,}drive and {allwinner,}pull for drive/bias setting, while newer DTS is using drive-strength and bias-{disable,pull-up,pull-down} properties. Accept these properties as well.
Additionally make bias and drive strength optional rather than required; not setting them should just indicate that we do not need to configure these properties.
Tested on: Banana Pi-M3 (a83t)
Obtained from: NetBSD (partially)