Add the sysfs entry for dumpStats and clearStats.
Previously these commands would be queried via iwpriv
--> iwpriv wlan0 dumpStats [stats_id]
--> iwpriv wlan0 clearStats [stats_id]
it is now changed to support via sysfs:
--> echo [stats_id] > /sys/class/net/wlanxx/dump_stats
--> cat /sys/class/net/wlanxx/dump_stats
--> echo [stats_id] > /sys/class/net/wlanxx/clear_stats
Change-Id: If8e4d997bc621df98732461802fdd9cea89bd1ce
CRs-Fixed: 2685995
efc4350044