swr: update double precision checks for our resampler

It supports double precision since a while
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswresample/swresample.c

@@ -231,8 +231,9 @@ int swr_init(struct SwrContext *s){
     if(    s->int_sample_fmt != AV_SAMPLE_FMT_S16P
         && s->int_sample_fmt != AV_SAMPLE_FMT_S32P
         && s->int_sample_fmt != AV_SAMPLE_FMT_FLTP
+        && s->int_sample_fmt != AV_SAMPLE_FMT_DBLP
         && s->resample){
-        av_log(s, AV_LOG_ERROR, "Resampling only supported with internal s16/s32/flt\n");
+        av_log(s, AV_LOG_ERROR, "Resampling only supported with internal s16/s32/flt/dbl\n");
         return -1;
     }