mac80211: clean up ieee80211_hw_config errors

Warn when ieee80211_hw_config returns an error, it shouldn't
happen; remove a number of printks that would happen in such
a case and one printk that is user-triggerable.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>