Revert "f2fs: clean up with is_valid_blkaddr()"

This reverts commit a9a6eb48.

This is a preparation change for merging android-4.14 commit
73421a43 into msm-4.14 branch.
The reverted change is committed already as:

9e6c4a85 f2fs: clean up with is_valid_blkaddr()

Conflicts:
	fs/f2fs/checkpoint.c
	fs/f2fs/data.c
	fs/f2fs/f2fs.h
	fs/f2fs/recovery.c

Change-Id: Icffba5adb8e117081b6e34f9a2a89b3c5f1651aa
Signed-off-by: Blagovest Kolenichev <bkolenichev@codeaurora.org>