HWC: Use 2 VG pipes for YUV layer with width > 2048

To minimize usage of decimation when 4K x 2K video is played
on primary, split the yuv layer into 2 halves and configure
each layer to individual VG pipes. With this approach,
decimation can be avoided in some 4K x 2K video use cases,
thereby improving performance.

Change-Id: I7cddfab787c50f6ff132eaa7f5a3d9cfd636c282
4 files changed