avcodec/mjpegdec: simplify rgb index remaping

libavcodec/mjpegdec.c

@@ -1600,9 +1600,7 @@ int ff_mjpeg_decode_sos(MJpegDecodeContext *s, const uint8_t *mb_bitmask,
         s->h_scount[i]  = s->h_count[index];
         s->v_scount[i]  = s->v_count[index];
 
-        if(nb_components == 3 && s->nb_components == 3 && s->avctx->pix_fmt == AV_PIX_FMT_GBR24P)
-            index = (i+2)%3;
-        if(nb_components == 1 && s->nb_components == 3 && s->avctx->pix_fmt == AV_PIX_FMT_GBR24P)
+        if((nb_components == 1 || nb_components == 3) && s->nb_components == 3 && s->avctx->pix_fmt == AV_PIX_FMT_GBR24P)
             index = (index+2)%3;
 
         s->comp_index[i] = index;