fix(rss): fix build issues with comms protocol

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: I77d2d3c5ac39a840b768f84f859d76b3965749aa
diff --git a/drivers/arm/rss/rss_comms_protocol_embed.c b/drivers/arm/rss/rss_comms_protocol_embed.c
index fc348d2..d217340 100644
--- a/drivers/arm/rss/rss_comms_protocol_embed.c
+++ b/drivers/arm/rss/rss_comms_protocol_embed.c
@@ -5,7 +5,7 @@
  *
  */
 
-
+#include <assert.h>
 #include <string.h>
 
 #include <common/debug.h>