Adding image crypto digest commands to iPXE images

ipxe/local/general.h

@@ -1,3 +1,4 @@
+#define DIGEST_CMD            /* Image crypto digest commands */
 #define DOWNLOAD_PROTO_HTTPS  /* Secure Hypertext Transfer Protocol */      
 #define IMAGE_COMBOOT         /* COMBOOT */
 #define NET_PROTO_IPV6        /* IPv6 protocol */