boards: spresense: Add delay only for PMIC GPO setting

When RTC clock is still unstable, add a delay time only for PMIC GPO
setting to avoid a problem that the setting is not reflected.

boards/arm/cxd56xx/spresense/src/cxd56_power.c

@@ -206,9 +206,9 @@ int board_power_control(int target, bool en)
     {
       ret = pfunc(PMIC_GET_CH(target), en);
 
-      /* If RTC clock is unstable, delay 1 tick for PMIC setting. */
+      /* If RTC clock is unstable, delay 1 tick for PMIC GPO setting. */
 
-      if (!g_rtc_enabled)
+      if (!g_rtc_enabled && (PMIC_GET_TYPE(target) == PMIC_TYPE_GPO))
         {
           usleep(1);
         }