dt-bindings: sound: msm8916-wcd-analog: fix example regulator names

Fix upper-case regulator names in the binding example which do not match
the corresponding required properties.

While at it, add a blank line after the required-properties section to
improve readability.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>