mfd: ab8500: Rewrite bindings in YAML

This rewrites the former text based AB8500 bindings in YAML.

When the AB8500 bindings were first written (in 2012) we
were not strict on some things and node names were definitely
not standardized.

This patch uses standard node names to most of the subnodes
on the AB8500 and is accompanied by another patch fixing
all the DTS files to conform to this.

The bindings are not as perfect as newly written bindings
would be, it is a best effort to deal with the legacy.

Cc: devicetree@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220115002649.1526163-1-linus.walleij@linaro.org