Tidy comment

Signed-off-by: Graham MacDonald <[email protected]>

aarch64/src/vm.rs

@@ -482,10 +482,7 @@ pub unsafe fn init(kpage_table: &mut PageTable, dtb_range: PhysRange, available_
         write_volatile(&mut kpage_table.entries[511], entry);
     }
 
-    // TODO We don't actualy unmap the first page...  We should to achieve:
-    // Note that the first page is left unmapped to try and
-    // catch null pointer dereferences in unsafe code: defense
-    // in depth!
+    // TODO leave the first page unmapped to catch null pointer dereferences in unsafe code
     let custom_map = {
         let text_range =
             PhysRange(from_virt_to_physaddr(text_addr())..from_virt_to_physaddr(etext_addr()));