mailbox_capsule: plumb attached page on recv

Change the message recv callback to pass an optionally received page
(part of the revised mailbox protocol).

Bug: 294433731

Change-Id: I201b69b44be504dd9b1610fc94968080d3b7d691

capsules/src/mailbox_capsule.rs

diff --git a/capsules/src/mailbox_capsule.rs b/capsules/src/mailbox_capsule.rs
index d0e4206..842a16a 100644
--- a/capsules/src/mailbox_capsule.rs
+++ b/capsules/src/mailbox_capsule.rs
@@ -183,8 +183,9 @@
                         // schedule the app callback.
                         match mailbox.get_message_slice_sync(&buffer) {
                             Ok(len) => {
+                                let page = mailbox.get_message_page().unwrap_or(0);
                                 app_data.recv_callback.map(|mut callback| {
-                                    callback.schedule(1, len, 0);
+                                    callback.schedule(1, len, page as usize);
                                 });
                             }
                             Err(len) => {