configure: enable ffnvcodec, nvenc, nvdec for FreeBSD

Signed-off-by: Brad Smith <brad@comstyle.com>

configure

@@ -7350,7 +7350,7 @@ fi
 
 if enabled x86; then
     case $target_os in
-        mingw32*|mingw64*|win32|win64|linux|cygwin*)
+        freebsd|mingw32*|mingw64*|win32|win64|linux|cygwin*)
             ;;
         *)
             disable ffnvcodec cuvid nvdec nvenc