ARM: dts: msm: Configure LDO7 as a parent to LDO4 for trinket

On trinket UFS platform, LDO7 (USB 0.9V) is affecting UFS and
resulting in UFS failures when USB is removed(LDO7 off).
This change configures LDO7 as a parent-supply to LDO4 as per
power grid scheme to make sure LDO7 is turned off only if LDO4
is off.

Change-Id: Ief210254126fd269699ca23eb22800e3b4fc1000
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>