Fix to return -ENOMEM in the kset create and add error handling
case instead of 0, as done elsewhere in this function.

Introduced by commit b59d0bae.
(f2fs: add sysfs support for controlling the gc_thread)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: NNamjae Jeon <namjae.jeon@samsung.com>
[Jaegeuk Kim: merge the patch with previous modification]
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>