avformat/hls: fix missing segment offset reset on last segment when http_multiple is enabled.

Reviewed-by: Steven Liu <lq@onvideo.cn>
Signed-off-by: vectronic <hello.vectronic@gmail.com>

libavformat/hls.c

@@ -1449,6 +1449,7 @@ reload:
 
         if (c->http_multiple == 1 && v->input_next_requested) {
             FFSWAP(AVIOContext *, v->input, v->input_next);
+            v->cur_seg_offset = 0;
             v->input_next_requested = 0;
             ret = 0;
         } else {