Remove unused suspend_idle (#16063)

platforms/avr/suspend.c

@@ -16,19 +16,6 @@
 #    include "vusb.h"
 #endif
 
-/** \brief Suspend idle
- *
- * FIXME: needs doc
- */
-void suspend_idle(uint8_t time) {
-    cli();
-    set_sleep_mode(SLEEP_MODE_IDLE);
-    sleep_enable();
-    sei();
-    sleep_cpu();
-    sleep_disable();
-}
-
 // TODO: This needs some cleanup
 
 #if !defined(NO_SUSPEND_POWER_DOWN) && defined(WDT_vect)