Drop todo note on num_pages

Co-authored-by: Martin Kröning <mkroening@posteo.net>

Author: hcsch

src/balloon.rs

@@ -19,7 +19,7 @@ use crate::le32;
 #[derive(VolatileFieldAccess)]
 #[repr(C)]
 pub struct Config {
-    #[access(ReadOnly)] // TODO: Not actually specified by the spec?
+    #[access(ReadOnly)]
     num_pages: le32,
 
     #[access(ReadWrite)]