f2fs: introduce help macro ADDRS_PER_PAGE()

Introduce help macro ADDRS_PER_PAGE() to get the number of address pointers in
direct node or inode.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

diff --cc fs/f2fs/data.c
Simple merge

diff --cc fs/f2fs/file.c
Simple merge

diff --cc fs/f2fs/recovery.c
Simple merge

diff --cc include/linux/f2fs_fs.h
Simple merge