Revert "seq_file: always clear m->count when we free m->buf"

This reverts commit 5e776c06ba6b6985940e842f48e6dc683998d12f.
Revert "seq_file: always update file->f_pos in seq_lseek()"

This reverts commit ae31a4f159ec83d318848ce01c3beb754a5e1df5.
Build v3.71