hwc: Handle multiple YUV layer use case in low end targets

In low end targets with one VG pipe, when there are more than one
YUV layer in the layer list, configure one YUV layer (bottom most)
to VG pipe, instead of falling back to GPU completely.

Change-Id: I5c78613573c4ebfbda3a729245092cc635ef8b98
1 file changed