test(realm): fix realm_printf string

Remove extra Realm: string from realm printf
correct the print format

Change-Id: I1916cf5bda23aab2cdee59457872353c108148c7
Signed-off-by: Shruti Gupta <shruti.gupta@arm.com>
diff --git a/realm/realm_payload_main.c b/realm/realm_payload_main.c
index e1f78c5..563c643 100644
--- a/realm/realm_payload_main.c
+++ b/realm/realm_payload_main.c
@@ -29,7 +29,7 @@
 {
 	uint64_t sleep = realm_shared_data_get_my_host_val(HOST_ARG1_INDEX);
 
-	realm_printf("Realm: going to sleep for %llums\n", sleep);
+	realm_printf("going to sleep for %llums\n", sleep);
 	waitms(sleep);
 }