drm/vmwgfx: Fix surface framebuffer check for guest-backed surfaces
drm/vmwgfx: Fix surface framebuffer check for guest-backed surfaces

With guest-backed surfaces, surface->sizes == NULL, causing a kernel oops.
Use the base_size member instead.

Signed-off-by: Thomas Hellstrom <a26490dfbee4be3d38287ad6448444504f58193c@vmware.com>
Reviewed-by: Jakob Bornecrantz <6c68cabc7124e43c9b4d50f86510600f69e74c99@vmware.com>
Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs