libmemif: fix implicit declaration of memfd_create

Change-Id: Icdeaad1d5df63bd5e9426958a3b73582bbd226b7
Signed-off-by: Jakub Grajciar <jgrajcia@cisco.com>
diff --git a/extras/libmemif/src/main.c b/extras/libmemif/src/main.c
index d0c1087..6048e4e 100644
--- a/extras/libmemif/src/main.c
+++ b/extras/libmemif/src/main.c
@@ -44,6 +44,7 @@
 #include <sys/timerfd.h>
 #include <sys/epoll.h>
 #include <signal.h>
+#include <linux/memfd.h>
 
 /* memif protocol msg, ring and descriptor definitions */
 #include <memif.h>