libf2fs: Track AOSP libsparse API change.

libf2fs: Track AOSP libsparse API change.

The libsparse in AOSP is updating the type for 'len', from 'int' to
'size_t', in the callback parameter of sparse_file_foreach_chunk(). The
value represents a chunk size, which could be legitimately larger than
INT_MAX. This patch tracks the libsparse API change.

The change is guarded with SPARSE_CALLBACK_USES_SIZE_T that's exposed as
part of the libsparse change. This allows f2fs-tools to keep working
against older libsparse versions.

Signed-off-by: Tao Bao <tbao@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>