cactus: ivy: Add sleep service

This service sleeps for a number of milliseconds.

Change-Id: Ib7f17142d22c8313dedc5f8037874bacbf8ed5f4
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/spm/ivy/ivy_def.h b/spm/ivy/ivy_def.h
index 11eeacf..729c46d 100644
--- a/spm/ivy/ivy_def.h
+++ b/spm/ivy/ivy_def.h
@@ -41,6 +41,8 @@
 #define IVY_PRINT_MAGIC			U(1001)
 /* Return a magic number unique to IVY */
 #define IVY_GET_MAGIC			U(1002)
+/* Sleep for a number of milliseconds */
+#define IVY_SLEEP_MS			U(1003)
 
 #define IVY_MAGIC_NUMBER		U(0x97531842)