dt-bindings: regulator/mfd: Reorganize S2MPA01 bindings

The mfd/s2mpa01.txt duplicates some of the information about bindings
with old mfd/s2mps11.txt. Now common part exists entirely in
mfd/samsung,sec-core.txt so:
 - add company prefix to file name (regulator/samsung,s2mpa01.txt),
 - remove duplicated information,
 - reorganize the contents to match style of
   regulator/samsung,s2mps11.txt.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>