regulator: da9055: Pass descriptor instead of GPIO number

When setting up a fixed regulator on the DA9055, pass a descriptor
instead of a global GPIO number. This facility is not used in the
kernel so we can easily just say that this should be a descriptor
if/when put to use.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>