f2fs: fix to remove redundant SBI_NEED_FSCK flag set

Subsequent f2fs_stop_checkpoint will set cp_err, so this
SBI_NEED_FSCK flag set action is invalid.

Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>