regulator: s5m8767: Update s5m8767-regulator bindings document

s5m8767 regulator is used on Exynos platforms which use pin controller
to configure GPIOs. Update the example accordingly.

[This had previously been broken by code changes which failed to update
the documentation -- broonie]

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>