leds: wm831x-status: Request a REG resource

The wm831x-status driver was not converted to use a REG resource when they
were introduced and the rest of the wm831x drivers converted, causing it
to fail to probe due to requesting the wrong resource type.

Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org # v3.7+
Signed-off-by: Bryan Wu <cooloney@gmail.com>