ARM: dts: msm: switch to RPMh controlled PMIC regulators for sdxprairie

Replace the stub-regulator device nodes for the pmxprairie
regulators with rpmh-regulator device nodes.  This ensures that
consumers are able to modify the physical state of these PMIC
regulators.

Also update the minimum and maximum voltages allowed for each
regulator to match the most recently documented limits.  These
limits are enforced by the AOP.

Change-Id: I51fca2acc51389b54c122a9ead32ab7f92941f09
Signed-off-by: David Collins <collinsd@codeaurora.org>