ARM: dts: msm: switch regulators to RPM control for msm8939

Switch qpnp-regulator devices to rpm-smd-regulator devices for msm8939.
This make sure the requests for these regulators are sent to RPM
processor for handling.

Remove the stub regulator devices defined in msm8939-rumi.dts to avoid
the duplicate labels.

Change-Id: I0675d4436e2c761a9391ce349477ec544ec0fd42
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>