ARM: dts: msm: Proxy vote for DSI regulators

This change adds proxy vote for all DSI regulators. This is
needed to keep display alive during boot up when continuous
splash is enabled.

Change-Id: Id186fa9efde87e7aa90834822a9ad87497e4cfe7
Signed-off-by: Satya Rama Aditya Pinapala <psraditya30@codeaurora.org>