dri: in swrast use render nodes and custom VGEM dump map ioctl

BUG=chromium:469666
TEST=boot freon ChromeOS under qemu and see the UI
CQ-DEPEND=CL:262952,CL:263990,CL:264000,CL:263991

Change-Id: Ie2b24dc416eef5e8fbc4395db5142b3d960285d6
1 file changed