pw_spin_delay_pico: Implement Micros

Implemented microsecond delay function.

Change-Id: Ic33d74d27989ce5a75802be7c1b1d06e8b7b870c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/125610
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
Commit-Queue: Chris Mumford <cmumford@google.com>
diff --git a/pw_spin_delay_pico/delay.cc b/pw_spin_delay_pico/delay.cc
index cfb310d..5d8cf56 100644
--- a/pw_spin_delay_pico/delay.cc
+++ b/pw_spin_delay_pico/delay.cc
@@ -22,6 +22,6 @@
 
 void WaitMillis(size_t delay_ms) { sleep_ms(delay_ms); }
 uint32_t Millis() { return to_ms_since_boot(get_absolute_time()); }
-uint32_t Micros() { return 0; }
+uint32_t Micros() { return to_us_since_boot(get_absolute_time()); }
 
 }  // namespace pw::spin_delay