hardware/qcom/display: Remove glfinish call

There is no need to do a glFinish on every composition complete.
glFinish needs to be called for composition cycles where GPU and
copybit are both used for composition. This is because the GPU and
copybit operate on the same framebuffer.

(cherry picked from commit 7983c275ae3eb15fab931d301e6338f83ad4a75a)

Change-Id: If06da4ca60ec17122c3dd698558cbf08fec73251