conman:  Use --width 80 on Frenzy.

Frenzy devices should specify a channel width of 80 when joining the
WLAN.  If not available, they will use the largest available width.

BUG=29102355

Change-Id: I0563697df588e011dcdde4a71b38d05332389e57
diff --git a/wifi/quantenna.py b/wifi/quantenna.py
index 6c68029..f4edc4d 100755
--- a/wifi/quantenna.py
+++ b/wifi/quantenna.py
@@ -88,7 +88,7 @@
   _qcsapi('restore_default_config', 'noreboot')
 
   config = {
-      'bw': opt.width,
+      'bw': opt.width if mode == 'ap' else 80,
       'channel': 149 if opt.channel == 'auto' else opt.channel,
       'mode': mode,
       'pmf': 0,