ARM: dts: msm: abstract lt9611 vcc as a fixed-regulator

In RD-LC device lt9611 vcc is supplied by a LDO which
is controlled by TLMM GPIO, so abstract it as a fixed
regulator for better management over power up sequence.

CRs-Fixed: 2186423
Change-Id: I02a7cbc01ece4432a96009d81f43f319fcbc3f02
Signed-off-by: Ray Zhang <rayz@codeaurora.org>