nl80211/cfg80211: Add support to disable CCK rate for management frame

Add a new nl80211 attribute to specify whether to send the management
frames in CCK rate or not. As of now the wpa_supplicant is disabling
CCK rate at P2P init itself. So this patch helps to send P2P probe
request/probe response/action frames being sent at non CCK rate in 2GHz
without disabling 11b rates.

This attribute is used with NL80211_CMD_TRIGGER_SCAN and
NL80211_CMD_FRAME commands to disable CCK rate for management frame
transmission.

Cc: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>