risc-v: Support cpu activity led in up_idle

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

arch/risc-v/src/common/riscv_idle.c

@@ -25,6 +25,8 @@
 #include <nuttx/config.h>
 #include <nuttx/irq.h>
 #include <nuttx/arch.h>
+#include <nuttx/board.h>
+#include <arch/board/board.h>
 
 #include "riscv_internal.h"
 
@@ -55,6 +57,14 @@ void up_idle(void)
   nxsched_process_timer();
 #else
 
+  /* Does the board support an IDLE LED to indicate that the board is in the
+   * IDLE state?
+   */
+
+#ifdef CONFIG_ARCH_LEDS_CPU_ACTIVITY
+  board_autoled_off(LED_CPU);
+#endif
+
   /* This would be an appropriate place to put some MCU-specific logic to
    * sleep in a reduced power mode until an interrupt occurs to save power
    */