devices: rtc_pl031: drop TimstampUs

It is not used anywhere in code.

Signed-off-by: Wei Liu <liuwe@microsoft.com>

devices/src/legacy/rtc_pl031.rs

@@ -153,24 +153,6 @@ impl fmt::Display for LocalTime {
     }
 }
 
-/// Holds a micro-second resolution timestamp with both the real time and cpu time.
-#[derive(Clone)]
-pub struct TimestampUs {
-    /// Real time in microseconds.
-    pub time_us: u64,
-    /// Cpu time in microseconds.
-    pub cputime_us: u64,
-}
-
-impl Default for TimestampUs {
-    fn default() -> TimestampUs {
-        TimestampUs {
-            time_us: get_time(ClockType::Monotonic) / 1000,
-            cputime_us: get_time(ClockType::ProcessCpu) / 1000,
-        }
-    }
-}
-
 /// Returns a timestamp in nanoseconds based on the provided clock type.
 ///
 /// # Arguments