fix(pycardium): Remove unnecessary libc stubs

Signed-off-by: Rahix <rahix@rahix.de>

pycardium/mphalport.c

@@ -65,22 +65,3 @@ mp_obj_t mp_builtin_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs)
 	return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
-
-/******************************************************************************
- * TODO: Remove
- */
-
-int _getpid(void)
-{
-	return -1;
-}
-
-int _kill(int pid, int f)
-{
-	return -1;
-}
-
-void _exit(int r)
-{
-	;
-}