chore: add default group automatly if needed

the name of the default group is the same with
the directory name.

Signed-off-by: Caoruihong <crh.cao@huawei.com>
Change-Id: I3d889a361534adc44e3b1bedfec13efe8e1babf2

arch/arm/arm/BUILD.gn

@@ -70,10 +70,6 @@ kernel_module(module_name) {
   public_configs = [ ":public" ]
 }
 
-group("arm") {
-  public_deps = [ ":$module_name" ]
-}
-
 config("public") {
   include_dirs = [
     "include",