[v3.13][v3.14][Regression] kthread: make kthread_create() killable

[Tetsuo Handa]

Joseph Salisbury wrote:
> A kernel bug report was opened against Ubuntu[0].  We performed a kernel
> bisect, and found that reverting the following commit resolved this bug:

I added a comment to that bug report.

This commit by chance revealed incorrect error handling of mptsas_probe() or
mptscsih_remove().