greybus: arche-platform: propagate errors returned by gpiolib

Propagate errors returned by of_get_named_gpio() instead of sending
-ENODEV.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>