Staging: rt2870: Revert d44ca7 Removal of kernel_thread() API

Staging: rt2870: Revert d44ca7 Removal of kernel_thread() API

commit 2c63abf9e8a51dec886da482dfd8ae752581a61c upstream.

[Mike Galbraith did the upstream revert, which was more complex]

Staging: rt2870: Revert d44ca7 Removal of kernel_thread() API

The sanity check this patch introduced triggers on shutdown, apparently due to
threads having already exited by the time BUG_ON() is reached.

Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Teoh <htmldeveloper@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>