Standardise and require safety comments in vmbase.

Bug: 290018030
Test: m vmbase_example_bin
Change-Id: Ic5704d6cd9b2a4090fa9758d7a65a56e83c4286c
diff --git a/vmbase/src/console.rs b/vmbase/src/console.rs
index 7c8ddf6..f94feba 100644
--- a/vmbase/src/console.rs
+++ b/vmbase/src/console.rs
@@ -25,7 +25,7 @@
 
 /// Initialises a new instance of the UART driver and returns it.
 fn create() -> Uart {
-    // Safe because BASE_ADDRESS is the base of the MMIO region for a UART and is mapped as device
+    // SAFETY: BASE_ADDRESS is the base of the MMIO region for a UART and is mapped as device
     // memory.
     unsafe { Uart::new(BASE_ADDRESS) }
 }