usb: misc: onboard_usb_hub: Drop reset delay in onboard_hub_power_off()

onboard_hub_power_off() currently has a delay after asserting the
reset of the hub. There is already a delay in onboard_hub_power_on()
before de-asserting the reset, which ensures that the reset is
asserted for the required time, so the delay in _power_off() is not
needed.

Skip the reset GPIO check before calling gpiod_set_value_cansleep(),
the function returns early when the GPIO descriptor is NULL.

Reviewed-By: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Link: https://lore.kernel.org/r/20220805111836.1.Id5a4dc0a2c046236116693aa55672295513a0f2a@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>