regulator: qcom: Rework to single platform device

Modeling the individual RPM resources as platform devices consumes at
least 12-15kb of RAM, just to hold the platform_device structs. Rework
this to instead have one device per pmic exposed by the RPM.

With this representation we can more accurately define the input pins on
the pmic and have the supply description match the data sheet.

Suggested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>