Change to DEVICE_CRYPTOCELL definition

Change `#if DEVICE_CRYPTOCELL` to `#if defined(DEVICE_CRYPTOPCELL)`

Author: Ron Eldor

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/objects.h

@@ -54,7 +54,7 @@ extern "C" {
 
 #include "nrf_uart.h"
 
-#if DEVICE_CRYPTOCELL
+#if defined(DEVICE_CRYPTOCELL)
 #include "objects_cryptocell.h"
 #else
 struct trng_s {