arm: mvebu: dts: turris_mox: fix USB3 regulator

Commit e8e9715d requires the USB3 regulator node to have the
enable-active-high property for the regulator to work properly. The
GPIO_ACTIVE_HIGH constant is not enough anymore.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Fixes: e8e9715d ("regulator: fixed: Modify enable-active-high...")
Reviewed-by: Stefan Roese <sr@denx.de>