dt-bindings: qcom_spmi: Document PM8005 regulators

Document the dt bindings for the PM8005 regulators which are usually used
for VDD of standalone blocks on a SoC like the GPU.

Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>