rename wwan-related modules/services

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

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; };