inject.f2fs: add ssa injection

This patch enables injecting summary block or summary entry.
print_raw_sum_entry_info() and print_sum_footer_info() are added to show
values of the ssa entry and summary footer.

The meanings of options are:
 * ssa: means ssa entry is injected.

The members could be injected in cp contains:
 * entry_type: summary block footer entry_type
 * check_sum: summary block footer check_sum
 * nid: summary entry nid
 * version: summary entry version
 * ofs_in_node: summary entry ofs_in_node

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Sheng Yong <shengyong@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>