arm64: dts: qcom: sdm845-mtp: Add RPMh VRM/XOB regulators

Add regulator devices for PMIC regulators managed via VRM and XOB
RPMh accelerators.

A few notes here:
- Regulators are added directly to the board file.  While it's true
  that this will mean a bunch of copy/pasting for other boards that
  are very similar, this is probably the right call since boards
  could make changes to the way these regulators are hooked up and
  trying to find a way to avoid duplication will result in some
  confusing node overrides.
- Regulators that are hooked up to supply pins on the SoC are given
  an alias matching the name of that pin (pin name comes from the
  Qualcomm SoC "device specification" doc).
- Other regulator labels are based on the schematic.  If there is
  more than one logical name on the schematic for the same rail the
  secondary names are also listed and should be referred to as
  appropriate.
- Regulators all default to HPM mode w/ no ability to switch modes.
  Future patches can switch things to LPM and possibly add
  dynamic load switching if we have determined there's a benefit.
  This should only be done for rails where we'll actually be able
  to take advantage of the lower power modes so we don't need to
  churn with lots of patches adding regulator_set_load() calls
  to drivers.

NOTE: This patch is loosely based on one originally shared to me by
David Collins.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>