Revert "f2fs: put allocate_segment after refresh_sit_entry"

Revert "f2fs: put allocate_segment after refresh_sit_entry"

commit c6f82fe90d7458e5fa190a6820bfc24f96b0de4e upstream.

This reverts commit 3436c4bdb30de421d46f58c9174669fbcfd40ce0.

This makes a leak to register dirty segments. I reproduced the issue by
modified postmark which injects a lot of file create/delete/update and
finally triggers huge number of SSR allocations.

[Jaegeuk Kim: Change missing incorrect comment]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>