The LogiCVC display hardware block comes with GPIO capabilities
that must be exposed separately from the main driver (as GPIOs) for
use with regulators and panels. A syscon is used to share the same
regmap across the two drivers.

Add a minimalistic GPIO driver to drive these GPIOs, using a syscon
regmap when available.
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://lore.kernel.org/r/20191203141243.251058-5-paul.kocialkowski@bootlin.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>