vd_lavc: let --hwdec=auto select "vaapi-copy"

Instead of "vaapi", simply by changing the probe order.

"vaapi" uses the GLX GL interop, which has causing us more problems than
it solved.

Unfortunately this leads also to copying if "--hwdec=auto --vo=vaapi" is
used, even though GLX is not involved in this case - but I don't care
enough to make the probe logic cleverer just for this. You can still get
the zero-copy path with --hwdec=vaapi.

(cherry picked from commit 27b5492a82)

video/decode/vd_lavc.c

@@ -130,8 +130,8 @@ static const struct vd_lavc_hwdec *const hwdec_list[] = {
     &mp_vd_lavc_vda,
 #endif
 #if HAVE_VAAPI_HWACCEL
-    &mp_vd_lavc_vaapi,
     &mp_vd_lavc_vaapi_copy,
+    &mp_vd_lavc_vaapi,
 #endif
 #if HAVE_DXVA2_HWACCEL
     &mp_vd_lavc_dxva2_copy,