f2fs: fix to check return value of inc_valid_block_count()

f2fs: fix to check return value of inc_valid_block_count()

In __replace_atomic_write_block(), we missed to check return value
of inc_valid_block_count(), for extreme testcase that f2fs image is
run out of space, it may cause inconsistent status in between SIT
table and total valid block count.

Cc: Daeho Jeong <daehojeong@google.com>
Fixes: 3db1de0e582c ("f2fs: change the current atomic write way")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>