fix: docs missed in riscv_goldfish

crates/riscv_goldfish/src/lib.rs

@@ -19,7 +19,7 @@ impl Rtc {
         Rtc { base_address }
     }
 
-    // Returns the current time in seconds since UNIX epoch.
+    /// Returns the current time in seconds since UNIX epoch.
     pub fn get_unix_timestamp(&self) -> u64 {
         const NSEC_PER_SEC: u64 = 1_000_000_000;