!188 fix an inappropriate errno in FatFs.

Merge pull request !188 from JING/master

fs/fat/os_adapt/fatfs.c

@@ -93,10 +93,13 @@ int fatfs_2_vfs(int result)
 
         case FR_NO_FILE:
         case FR_NO_PATH:
-        case FR_NO_FILESYSTEM:
             status = ENOENT;
             break;
 
+        case FR_NO_FILESYSTEM:
+            status = ENOTSUP;
+            break;
+
         case FR_INVALID_NAME:
             status = EINVAL;
             break;