mac80211: don't assume driver has been attached on registration

mac80211's ieee80211_register_hw() is often called within the
probe path so it cannot assume the device's driver structure
has been attached yet so to create a workqueue instead of
using driver->name use the wiphy's phy%d name. The name doesn't
really matter anyway.

This should fix sporadic oopses found when we race to beat the
driver pointer setting. Not even sure how this was working properly.

http://www.kerneloops.org/search.php?search=ieee80211_register_hw



Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>