dv1394 is disabled by default, do not redundantly disable it on Hurd.

Originally committed as revision 18946 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1698,7 +1698,6 @@ case $target_os in
     gnu/kfreebsd)
         ;;
     gnu)
-        disable dv1394
         ;;
 
     *)