cfg80211: make wiphy index start at 0 again

The change to use atomic_inc_return() for assigning the wiphy
index made the first wiphy index 1 instead of 0. This is fine,
but we all habitually type "phy0" when we're testing, so make
it go back to 0 instead of 1 by subtracting 1 from the index.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -301,6 +301,9 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 		return NULL;
 	}
 
+	/* atomic_inc_return makes it start at 1, make it start at 0 */
+	rdev->wiphy_idx--;
+
 	/* give it a proper name */
 	dev_set_name(&rdev->wiphy.dev, PHY_NAME "%d", rdev->wiphy_idx);