MAINTAINERS: Match on allwinner keyword

Some drivers (phy, crypto, net) folders don't have sunxi in it but
allwinner. Add that keyword to match on it too.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://lore.kernel.org/r/20210331130830.64182-2-maxime@cerno.tech

Author: mripard

MAINTAINERS

@@ -1582,6 +1582,7 @@ F:	arch/arm64/boot/dts/allwinner/
 F:	drivers/clk/sunxi-ng/
 F:	drivers/pinctrl/sunxi/
 F:	drivers/soc/sunxi/
+N:	allwinner
 N:	sun[x456789]i
 N:	sun50i