added TL Mailbox initialization for STM32WB

embassy-stm32/src/tl_mbox/evt.rs

@@ -0,0 +1,8 @@
+/// the payload of [`Evt`] for a command status event
+#[derive(Copy, Clone)]
+#[repr(C, packed)]
+pub struct CsEvt {
+    pub status: u8,
+    pub num_cmd: u8,
+    pub cmd_code: u16,
+}