msm: cpr-regulator: add MX handling as dependency for VDD APC

It could be required for the memory power (MX) to be equal or
higher than VDD APC voltage in certain way. Add code to
handle this voltage dependency with the support for several
possible methods of dependencies. If no such requirement on
certain target, don't specify the MX regulator in device tree.

Change-Id: Iabc8abe3eda881a92304aeb8e1f98394c8938c67
Signed-off-by: Willie Ruan <wruan@codeaurora.org>