libs/kaptan-stm32f7: add I2C1 controller

libs/kaptan-stm32f7/src/stm32f722/time.rs

@@ -51,6 +51,16 @@ impl DwtMicrosecondClock {
         self.advance_to(DWT::cycle_count())
     }
 
+    /// Creates another independent reader for the same already-running DWT
+    /// counter. Each reader must be serviced often enough to observe wraps.
+    pub const fn fork(&self) -> Self {
+        Self {
+            cycles_per_microsecond: self.cycles_per_microsecond,
+            previous_cycles: self.previous_cycles,
+            elapsed_cycles: self.elapsed_cycles,
+        }
+    }
+
     fn advance_to(&mut self, current_cycles: u32) -> Timestamp {
         let elapsed = current_cycles.wrapping_sub(self.previous_cycles);
         self.previous_cycles = current_cycles;