hwcomposer: 8x10: increase frame buffer count to 3 for copybit

On 8x10, ppp composition is enabled.  For PPP blending operation,
it can take around 14-15ms. This results that when the frame is
given to the display for rendering, it can happen around the
vsync boundary.   While DMA does the page flipping, it makes sure
it happens on vsync boundary.  However, in the ppp case, the vsync
can be from the previous frame, not the new frame just delivered.
Because of that, there will be tearing.  Increase the buffer count
to 3 will resolve this issue, and improve the frame rate as well.

Change-Id: I53bff1a61b38eaecd286fdbe8a069522e28df6ba
1 file changed