greybus: arche-platform: Set direction of wake/detect gpio in poweroff fn

With support of interrupt based mechanism, gpio is not longer set to
output mode, so gpio_set_value won't work. So use
gpio_direction_output() fn in poweroff(), while setting value on
wake/detect line.

Testing Done: Tested on DB3.5 platform.

Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Reviewed-by: Michael Scott <michael.scott@linaro.org>
Tested-by: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>