f2fs_io: add flags parameter to fiemap subcommand

Add a flags parameter to the fiemap subcommand so that it can pass
FIEMAP_FLAG_SYNC, FIEMAP_FLAG_XATTR, and FIEMAP_FLAG_CACHE. Before
retrieving the fiemap, perform the corresponding actions based on
these flags, such as syncing data or preloading extents.

Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>