drm/vmwgfx: Fix command defines and checks

Make sure all guest-backed object commands are properly packed.
Have the command verifier treat uninitialized command entries as invalid
rather than dereferencing NULL pointers.

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

diff --cc drivers/gpu/drm/vmwgfx/svga3d_reg.h
Simple merge

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