Simplify HWC and FB hal check

Change-Id: I0d005e3bb092b75ba281b89bb4e86d534f7f23de
Select texture target based on pixel format

Adreno is not optimized for GL_TEXTURE_EXTERNAL_OES, making GPU
utilization (and power), high with GL_TEXTURE_EXTERNAL_OES for
RGB formats.

Change texture target from GL_EXTERNAL_TEXTURE_OES to dynamically
select between GL_EXTERNAL_TEXTURE_OES, and GL_TEXTURE_2D based
on the pixel format.

This change is done to reduce the composition time for 8x55

Change-Id: I89ab1d60b23eef55442a9fd338b2a05b3304ce61
surfaceflinger: Enable dithering if persist.sys.use_dithering=1|2

* Fixes color banding(1) and blur effect(2)

0 : surface doesn't need dithering
1 : enable dithering if necessary (default)
2 : enable dithering (always)