Revert "f2fs: fix to propagate return value of scan_nat_page()"

This reverts commit 130ad547.

This is a preparation change for merging android-4.14 commit
e6fa8a20 into msm-4.14 branch.
The reverted change is committed already as:

35387179 f2fs: fix to propagate return value of scan_nat_page()

Change-Id: Ic8a5872e7437ec0014b3bdca3193e137eede4cb7
Signed-off-by: Blagovest Kolenichev <bkolenichev@codeaurora.org>