drm/vmwgfx: Add debug message for layout change ioctl

Add debug code to check user-space layout change request.

Signed-off-by: Deepak Rawat <drawat@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>