imx8mp-venice-gw74xx: default USB1 to host mode

The GW74xx USB1 controller connects to a dual-role connector using a GPIO
for role detection via the usb-connector Linux driver (usb-conn-gpio.c).

This drive does not exist yet in U-Boot so for now we will just default
USB1 to host mode.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>