net/mac80211/: Use time_* macros

The functions time_before, time_before_eq, time_after, and time_after_eq are more robust for comparing jiffies against other values.

So following patch implements usage of the time_after() macro, defined at linux/jiffies.h, which deals with wrapping correctly

Cc: linux-wireless@vger.kernel.org
Signed-off-by: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: John W. Linville <linville@tuxdriver.com>