regulator: wm831x: Convert to use GPIO descriptors

This converts the Wolfson Micro WM831x DCDC converter to use
a GPIO descriptor for the GPIO driving the DVS pin.

There is just one (non-DT) machine in the kernel using this, and
that is the Wolfson Micro (now Cirrus) Cragganmore 6410 so we
patch this board to pass a descriptor table and fix up the driver
accordingly.

Cc: Charles Keepax <ckeepax@opensource.cirrus.com>
Cc: Richard Fitzgerald <rf@opensource.cirrus.com>
Cc: patches@opensource.cirrus.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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ChangeLog v1->v2:
- Use device name "wm831x-buckv.11" as described by Charles
- Use devm_gpiod_get() rather than the optional variant
3 files changed