f2fs: remove unnecessary goto statement

When base_addr is NULL, there is no need to call kzfree,
it should return -ENOMEM directly. Additionally, it is
better to initialize variable 'error' with 0.

Signed-off-by: Tiezhu Yang <kernelpatch@126.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>