Merge branch 'mrf24j40'

Alan Ott says:

====================
Fix race conditions in mrf24j40 interrupts

After testing with the betas of this patchset, it's been rebased and is
ready for inclusion.

David Hauweele noticed that the mrf24j40 would hang arbitrarily after some
period of heavy traffic.  Two race conditions were discovered, and the
driver was changed to use threaded interrupts, since the enable/disable of
interrupts in the driver has recently been a lighning rod whenever issues
arise related to interrupts (costing engineering time), and since threaded
interrupts are the right way to do it.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>