drm/vmwgfx: Hook up the prime ioctls

Also provide a completely dumb dma-buf ops implementation.
Once we have other virtual dma-buf aware devices, we need to provide
something better.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

diff --cc drivers/gpu/drm/vmwgfx/Makefile
Simple merge

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
Simple merge

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
Simple merge

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_prime.c
Simple merge