ARM: dts: msm: Add parent supply for oxili_gx GDSC on msmsamarium

Oxili_gx GDSC needs to turn on its parent supply when it's enabled.
Add relevant dt entry to model this dependency.

Change-Id: I972658b685821d75b0075852a3e7d67e89cdb6e2
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>