ARM: dts: msm: switch to RPM controlled regulators for msmcobalt

The RPM is available in standalone mode. Move the stub regulators
that should be controlled by the RPM under RPM control.

Use the new railway resources for core rails VDD_CX and VDD_MX.

CRs-Fixed: 887818
Change-Id: Ibe3feebc72753af6ca4cd7b129ea04ee5a5cdfec
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>