hwc: Use GPU Composition for 8x26 virtual dpy scaling case

For 8x26, if there is only one layer which needs scale for
secondary display, while no scale for primary display, DMA
pipe is occupied by primary. If layer changed and need to
fall back to GLES composition, virtual display lacks DMA
pipe and error is reported.

To avoid this case, use GPU composition for virtual display
scaling case on 8x26.

Change-Id: I42297a18006517532e30d1a01c67ff8ca187482a
1 file changed