hwc: Set GPU performance hint.

1. Set the GPU hint flag to high for MIXED/GPU composition only for
   first frame after MDP to GPU/MIXED mode transition.
2. Set the GPU hint to default if the current composition type is GPU
   due to idle fallback or MDP composition.

Change-Id: I208a778017435a5a4620142da9d9fb3c50e09155
4 files changed