fix `idle::Resources::new`

it assumed that all resources were "early" resources

examples/late-resources.rs

@@ -32,6 +32,11 @@ app! {
         static PORT: u16;
     },
 
+    idle: {
+        // Test that late resources can be used in idle
+        resources: [IP_ADDRESS],
+    }
+
     tasks: {
         SYS_TICK: {
             priority: 1,

macros/src/trans.rs

@@ -74,8 +74,14 @@ fn idle(
                     });
 
                     let _name = Ident::new(format!("_{}", name.as_ref()));
-                    rexprs.push(quote! {
+                    rexprs.push(if resource.expr.is_some() {
+                        quote! {
                             #name: &mut #super_::#_name,
+                        }
+                    } else {
+                        quote! {
+                            #name: #super_::#_name.as_mut(),
+                        }
                     });
                 } else {
                     rfields.push(quote! {