rename wwan-related modules/services

we only currently support huawei e3372/cdc ncm so let's make that
explicit in the naming

examples/l2tp.nix

@@ -39,7 +39,7 @@ in rec {
   };
 
   imports = [
-    ../modules/cdc-ncm
+    ../modules/wwan
     ../modules/network
     ../modules/vlan
     ../modules/ssh
@@ -50,7 +50,7 @@ in rec {
   ];
   hostname = "thing";
 
-  services.wwan = svc.wwan.build {
+  services.wwan = svc.wwan.huawei-e3372.build {
     apn = "data.uk";
     username = "user";
     password = "one2one";

modules/wwan/default.nix

@@ -8,7 +8,7 @@ in {
   ];
 
   options = {
-    system.service.wwan = mkOption {
+    system.service.wwan.huawei-e3372 = mkOption {
       type = liminix.lib.types.serviceDefn;
     };
   };
@@ -21,7 +21,7 @@ in {
     };
 
     # https://www.0xf8.org/2017/01/flashing-a-huawei-e3372h-4g-lte-stick-from-hilink-to-stick-mode/
-    system.service.wwan = config.system.callService ./wwan.nix {
+    system.service.wwan.huawei-e3372 = config.system.callService ./huawei-e3372.nix {
       apn = mkOption { type = types.str; };
       username = mkOption { type = types.str; };
       password = mkOption { type = types.str; };