display: Use single thread for FB post.

To support swapinterval zero a separate thread
was added to do the framebuffer post. Since we
are going to support the WAITFORVSYNC ioctl in HWC,
we can handle the zero swapinterval case there.

Change-Id: I39f960825ca4173f99a9895e0c132b70a7adccab
3 files changed