This kfree() is no longer needed after a79dc083d7 "f2fs: move
bio_private allocation out of f2fs_bio_alloc()".  The "bio->bi_private"
is NULL here so it's a no-op.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>