drm/vmwgfx: Support the NOP_ERROR command

Can be used by user-space applications to test and verify the kernel
command buffer error recovery functionality.

Malicious user-space apps could potentially use this command to slow down
graphics processing somewhat, but they could also accomplish the same thing
using a random malformed command so this should be considered safe.
At least as safe as it gets.

Signed-off-by: Thomas Hellstrom <[e-mail]>
Reviewed-by: Brian Paul <[e-mail]>
Reviewed-by: Sinclair Yeh <[e-mail]>

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

···
 		    true, false, true),
 	VMW_CMD_DEF(SVGA_3D_CMD_NOP, &vmw_cmd_ok,
 		    true, false, true),
+	VMW_CMD_DEF(SVGA_3D_CMD_NOP_ERROR, &vmw_cmd_ok,
+		    true, false, true),
 	VMW_CMD_DEF(SVGA_3D_CMD_ENABLE_GART, &vmw_cmd_invalid,
 		    false, false, true),
 	VMW_CMD_DEF(SVGA_3D_CMD_DISABLE_GART, &vmw_cmd_invalid,