mac80211: Add log message to ieee80211_restart_hw()

Add a log message to ieee80211_restart_hw() to highlight
that special codepath in the logs. This helps debugging
bugs in the rarely tested restart code.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>