nixos/hostapd: set default channel to auto (#342573)

Author: K900

nixos/modules/services/networking/hostapd.nix

@@ -235,7 +235,7 @@ in {
             };
 
             channel = mkOption {
-              default = 7;
+              default = 0;
               example = 11;
               type = types.int;
               description = ''