leds: leds-gpio: Allow compile test if !GPIOLIB

The GPIO subsystem provides dummy GPIO consumer functions if GPIOLIB is
not enabled. Hence drivers that depend on GPIOLIB, but use GPIO consumer
functionality only, can still be compiled if GPIOLIB is not enabled.

Relax the dependency of LEDS_GPIO on GPIOLIB if COMPILE_TEST is
enabled.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bryan Wu <cooloney@gmail.com>