f2fs: fix to check return value of f2fs_reserve_new_block()

Let's check return value of f2fs_reserve_new_block() in do_recover_data()
rather than letting it fails silently.

Also refactoring check condition on return value of f2fs_reserve_new_block()
as below:
- trigger f2fs_bug_on() only for ENOSPC case;
- use do-while statement to avoid redundant codes;

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>