Move ownership of MAC address randomization mask to scan params

This array can be freed either from the scan parameters or from
clearing the MAC address randomization parameters from the
wpa_supplicant struct. To make this ownership more clear, we have
each struct own its own copy of the parameters.

Signed-off-by: Eric Caruso <ejcaruso@chromium.org>

src/drivers/driver.h

@@ -517,7 +517,7 @@ struct wpa_driver_scan_params {
 	 * mac_addr - MAC address used with randomization. The address cannot be
 	 * a multicast one, i.e., bit 0 of byte 0 should not be set.
 	 */
-	const u8 *mac_addr;
+	u8 *mac_addr;
 
 	/**
 	 * mac_addr_mask - MAC address mask used with randomization.