configure: Disable DNN without backend

The DNN filters are useless without a backend.
This will also "fix" Coverity issues #1598288 and #1601718.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

configure

@@ -2850,8 +2850,8 @@ deflate_wrapper_deps="zlib"
 dirac_parse_select="golomb"
 dovi_rpudec_select="golomb"
 dovi_rpuenc_select="golomb"
-dnn_suggest="libtensorflow libopenvino libtorch"
 dnn_deps="avformat swscale"
+dnn_deps_any="libtensorflow libopenvino libtorch"
 error_resilience_select="me_cmp"
 evcparse_select="golomb"
 faandct_deps="faan"