Adding back blockdevice example after removing it for PR ARMmbed#7774. Target should be K64F

Author: Yossi Levy

tools/test/examples/examples.json

@@ -292,6 +292,19 @@
         "compile" : true,
         "export": true,
         "auto-update" : true
-    }      
+    },
+    {
+        "name": "mbed-os-example-blockdevice",
+        "github":"https://github.com/armmbed/mbed-os-example-blockdevice",
+        "mbed": [],
+        "test-repo-source": "github",
+        "features" : [],
+        "targets" : ["K64F"],
+        "toolchains" : [],
+        "exporters": [],
+        "compile" : true,
+        "export": true,
+        "auto-update" : true
+    }     
   ]
 }