pnpbios: propagate kthread_run() error

- Error code from kthread_run() is now returned in pnpbios_thread_init()

- Remove variable which always was 0.

Signed-off-by: Erik Ekman <erik@kryo.se>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>