usb: onboard-hub: Use devm API do automatically free the reset GPIO

usb: onboard-hub: Use devm API do automatically free the reset GPIO

The reset GPIO is obtained during driver probing by the function
devm_gpiod_get_optional, which means the GPIO will be automatically
freed when the device is removed. Because of this, explicit call
to free the reset GPIO in hub remove function is not needed.
To support the Managed device resources, the DEVRES config must
be enabled, otherwise the devres functions fall back to non-managed
variants. Set the necessary dependency to DEVRES in Kconfig.

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Lukasz Czechowski <lukasz.czechowski@thaumatec.com>