arm64: dts: allwinner: axp803: Add drivevbus regulator

Add reg_drivevbus regualtor for boards which are using
external regulator to drive the OTG VBus through N_VBUSEN
PMIC pin.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>