ARM: dts: msm: add power grid regulator phandles for SDM855

Add secondary phandles to each of the PM855, PM855L, and PM8009
regulator devices which match the naming scheme used in the
power grid hardware documentation.  This should help to alleviate
confusion between similarly named regulators on different PMICs
(e.g. pm855_l1 and pm855l_l1 vs L1A and L1C).

Also add tertiary phandles for VDD_CX, VDD_MX, and VDD_MMCX
supplies which each serve the same purpose for several
consumers.

Change-Id: I31ee440c566085ecf66892584f2d273666193bde
Signed-off-by: David Collins <collinsd@codeaurora.org>