usb: dwc3-generic: Ensure reset GPIO is configured as an output

GPIOD_ACTIVE_LOW is not enough to configure a GPIO as an output, we need
GPIOD_IS_OUT as well.

Fixes: b252d79b ("usb: dwc3: Add support to reset usb ULPI phy")
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>