libcopybit: draw full layer if dirty region list is long

1. Since blitting region by region by copybit is serial, if a layer has
long list of dirty regions, drawing full layer is optimal. Make blit
region same as display frame of layer.
2. Fix alpha for HWC_BLENDING_NONE layers

(cherry picked from commit 57f0723baf97d0f6499458d6764d1416baa18b4f)

Change-Id: Ib08a292e4845259cfb313ca07db34da9f9200dec
HWC/copybit : Add support for isFG in copybit

Some applications are sending the RGBA layer with constact alpha
0xFF and isOpaque=1. For these types of layer we are not getting
any wormHole regions.Hence we are seeing the previous content (framebuffer)
due to wrong selection of blending logic at kernel side.

For fixing these type of issues for MDP3 we are making Z order zero
layer as FG same as MDP4 to choose proper blending logic.

(cherry picked from commit 68a0f20dd31a753abdefd0be64287d93f03036cc)

Change-Id: I73bf70b066e680e30194d655b2f9e46bf4bc85e9
CRs-fixed: 405802
CRs-fixed: 406503
CRs-fixed: 386356