arm/dt: msm-gdsc: Remove unnecessary inclusion of skeleton.dtsi

skeleton.dtsi or skeleton64.dtsi should be included in the top-level
.dts file, and not in other included files, such as msm-gdsc.dtsi.

Change-Id: I95cf1a0a542fc3139eeefce851a04f154c68b9d9
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>