[libj6] Remove driver_main

The `driver_main` sinature was an alternate signature for `main`
implemented with weak symbols, but it causes linking issues when not
statically linked, and drivers are going to work differently soon
anyway. Just get rid of it for now.

src/libraries/j6/init.cpp

@@ -36,12 +36,18 @@ j6_find_first_handle(j6_object_type obj_type)
     return j6_handle_invalid;
 }
 
-extern "C" j6_init_args *
+const j6_init_args *
+j6_get_init_args()
+{
+    return &init_args;
+}
+
+extern "C" void
 __init_libj6(uint64_t arg0, uint64_t arg1)
 {
     init_args.args[0] = arg0;
     init_args.args[1] = arg1;
-    return &init_args;
 }
 
+
 #endif // __j6kernel