tests: benchmarks: multicore: idle_spim: radio sleeps forever

Do not wakeup radio as it make current measurements noisy.

Signed-off-by: Piotr Kosycarz <[email protected]>

tests/benchmarks/multicore/idle_spim/remote/src/main.c

@@ -8,10 +8,7 @@
 
 int main(void)
 {
-	k_msleep(500);
-	while (1) {
-		k_msleep(2000);
-	}
+	k_sleep(K_FOREVER);
 
 	return 0;
 }