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

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

While at it, use stub regulator devices for sdxpoorwills-rumi because
RPMh based regulators are not supported on this platform.

CRs-Fixed: 2136750
Change-Id: I6d5f1e07bc0d1ce7e2294b3be39e8028cdbe3945
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>