arm/dt: msm8226: Stop sharing the GPU DTS file with 8974

It was becoming unwieldy to try to share GPU settings between 8974
and 8226 while accounting for differences like the different number
of power levels for each core.  Make 8226 into a standalone DTS file.

Change-Id: Ic0dedbadb46fd7704a8e6b347d66c6b3a04035d3
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>