[Core] Simplify audio_duration_to_ms() and audio_ms_to_duration(), reduce firmware size by a few bytes. (#21427)

platforms/test/drivers/audio_pwm_hardware.c

@@ -0,0 +1,20 @@
+// Copyright 2023 Google LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include "audio.h"
+
+void audio_driver_initialize(void) {}
+void audio_driver_start() {}
+void audio_driver_stop() {}