configure: Add explicit dsputil dependency to mpegvideoenc

Previously, it was an implicit dependency through mpegvideo. Change
this, as implicit dependencies can cause all sorts of trouble.

configure

@@ -1646,7 +1646,7 @@ rdft_select="fft"
 mpegaudio_select="mpegaudiodsp"
 mpegaudiodsp_select="dct"
 mpegvideo_select="dsputil hpeldsp videodsp"
-mpegvideoenc_select="mpegvideo"
+mpegvideoenc_select="dsputil mpegvideo"
 
 # decoders / encoders
 aac_decoder_select="mdct sinewin"