Remove Linuxisms from usage()

--- wpa_supplicant/main.c.orig	Mon Oct  3 11:10:23 2016
+++ wpa_supplicant/main.c	Mon Oct  3 11:11:42 2016
@@ -66,7 +66,7 @@ static void usage(void)
 	       "  -c = Configuration file\n"
 	       "  -C = ctrl_interface parameter (only used if -c is not)\n"
 	       "  -d = increase debugging verbosity (-dd even more)\n"
-	       "  -D = driver name (can be multiple drivers: nl80211,wext)\n"
+	       "  -D = driver name\n"
 	       "  -e = entropy file\n"
 #ifdef CONFIG_DEBUG_FILE
 	       "  -f = log output to debug file instead of stdout\n"
@@ -105,8 +105,7 @@ static void usage(void)
 	       "  -W = wait for a control interface monitor before starting\n");
 
 	printf("example:\n"
-	       "  wpa_supplicant -D%s -iwlan0 -c/etc/wpa_supplicant.conf\n",
-	       wpa_drivers[0] ? wpa_drivers[0]->name : "nl80211");
+	       "  wpa_supplicant -D openbsd -i athn0 -c /etc/wpa_supplicant.conf\n");
 #endif /* CONFIG_NO_STDOUT_DEBUG */
 }