We had better return the 'err' value when calling kstrtoul() failed, so
the user will know why it really fails, there do little change, let it
return the 'err' value when failed.

Link: https://lkml.kernel.org/r/6329ebe0.050a0220.ec4bd.297cSMTPIN_ADDED_BROKEN@mx.google.comSuggested-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>