system/core: vold: Change permission of external storage device nodes

Signed-off-by: San Mehat <san@google.com>
diff --git a/vold/blkdev.c b/vold/blkdev.c
index 1482a1a..e10eafc 100644
--- a/vold/blkdev.c
+++ b/vold/blkdev.c
@@ -219,7 +219,7 @@
 
     /* Create device nodes */
     char nodepath[255];
-    mode_t mode = 0666 | S_IFBLK;
+    mode_t mode = 0660 | S_IFBLK;
     dev_t dev = (major << 8) | minor;
 
     sprintf(nodepath, "%s/vold/%d:%d", DEVPATH, major, minor);