Make preprocessor condition more specific and useful by changing

#ifdef CONFIG_ENCODERS --> #ifdef CONFIG_DVVIDEO_ENCODER.

Originally committed as revision 14165 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/dv.c

@@ -1000,7 +1000,7 @@ static int dv_decode_mt(AVCodecContext *avctx, void* sl)
     return 0;
 }
 
-#ifdef CONFIG_ENCODERS
+#ifdef CONFIG_DVVIDEO_ENCODER
 static int dv_encode_mt(AVCodecContext *avctx, void* sl)
 {
     DVVideoContext *s = avctx->priv_data;