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

Add secondary phandles to each of the PM855 (1), PM855 (2), and
PM855P 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_1_l5 and pm855_2_l5 vs L5A and L5E).

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

Change-Id: Ie22070775200841d9fcc518d1ad69a82765c846c
Signed-off-by: David Collins <collinsd@codeaurora.org>