cfg80211: fix elapsed_jiffies calculation

MAX_JIFFY_OFFSET has no meaning when calculating the
elapsed jiffies, as jiffies run out until ULONG_MAX.

This miscalculation results in erroneous values
in case of a wrap-around.
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.h

@@ -424,7 +424,7 @@ static inline unsigned int elapsed_jiffies_msecs(unsigned long start)
 	if (end >= start)
 		return jiffies_to_msecs(end - start);
 
-	return jiffies_to_msecs(end + (MAX_JIFFY_OFFSET - start) + 1);
+	return jiffies_to_msecs(end + (ULONG_MAX - start) + 1);
 }
 
 void