avformat/matroskaenc: Clean up mkv_write_stereo_mode()

Mostly reindentation after the last commit. Also remove a variable that
is always zero; move another variable to a more local scope and don't
assign a value to a local variable immediately before leaving the function.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/matroskaenc.c

@@ -1025,8 +1025,6 @@ static void mkv_write_field_order(AVIOContext *pb, int mode,
 static int mkv_write_stereo_mode(AVFormatContext *s, AVIOContext *pb,
                                  AVStream *st, int mode, int *h_width, int *h_height)
 {
-    int i;
-    int ret = 0;
     const AVDictionaryEntry *tag;
     MatroskaVideoStereoModeType format = MATROSKA_VIDEO_STEREOMODE_TYPE_NB;
     const AVStereo3D *stereo;
@@ -1039,7 +1037,7 @@ static int mkv_write_stereo_mode(AVFormatContext *s, AVIOContext *pb,
         (tag = av_dict_get( s->metadata, "stereo_mode", NULL, 0))) {
         int stereo_mode = atoi(tag->value);
 
-        for (i=0; i<MATROSKA_VIDEO_STEREOMODE_TYPE_NB; i++)
+        for (int i = 0; i < MATROSKA_VIDEO_STEREOMODE_TYPE_NB; i++)
             if (!strcmp(tag->value, ff_matroska_video_stereo_mode[i])){
                 stereo_mode = i;
                 break;
@@ -1098,7 +1096,7 @@ static int mkv_write_stereo_mode(AVFormatContext *s, AVIOContext *pb,
     }
 
     if (format == MATROSKA_VIDEO_STEREOMODE_TYPE_NB)
-        return ret;
+        return 0;
 
     // if webm, do not write unsupported modes
     if ((mode == MODE_WEBM &&
@@ -1107,14 +1105,13 @@ static int mkv_write_stereo_mode(AVFormatContext *s, AVIOContext *pb,
         || format >= MATROSKA_VIDEO_STEREOMODE_TYPE_NB) {
         av_log(s, AV_LOG_ERROR,
                "The specified stereo mode is not valid.\n");
-        format = MATROSKA_VIDEO_STEREOMODE_TYPE_NB;
         return AVERROR(EINVAL);
     }
 
     // write StereoMode if format is valid
     put_ebml_uint(pb, MATROSKA_ID_VIDEOSTEREOMODE, format);
 
-    return ret;
+    return 0;
 }
 
 static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,