Nenik: Re-enable SD specific sleep path, related to #165

When the SoftDevice is active (e.g. as soon as you call Bluefruit.begin()),
standby by __WFE seems to keep external Xtal oscillator running
(at least on nRF52832), increasing the standby power consumption
by 500-800uA. The SD-enabled path was apparently disabled mistakenly
by Nordic, see Nordic post for reference:
https://devzone.nordicsemi.com/f/nordic-q-a/35073/high-power-consumption-of-softdevice/136048#136048

Author: Nenik

cores/nRF5/freertos/portable/CMSIS/nrf52/port_cmsis_systick.c

@@ -182,7 +182,6 @@ void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
         configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
         if ( xModifiableIdleTime > 0 )
         {
-#if 0  // With FreeRTOS sd_app_evt_wait increases power consumption with FreeRTOS compared to _WFE (NRFFOSDK-11174)
 #ifdef SOFTDEVICE_PRESENT // TODO
             uint8_t sd_en = 0;
             (void) sd_softdevice_is_enabled(&sd_en);
@@ -193,7 +192,6 @@ void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
             }
             else
 #endif
-#endif // (NRFFOSDK-11174)
             {
                 /* No SD -  we would just block interrupts globally.
                 * BASEPRI cannot be used for that because it would prevent WFE from wake up.