fs: yaffs2: Make yaffsfs_deviceList static

yaffsfs_deviceList is only referenced in yaffsfs.c

Signed-off-by: Bin Meng <bmeng@tinylab.org>
diff --git a/fs/yaffs2/yaffsfs.c b/fs/yaffs2/yaffsfs.c
index 510faae..d615f02 100644
--- a/fs/yaffs2/yaffsfs.c
+++ b/fs/yaffs2/yaffsfs.c
@@ -468,7 +468,7 @@
 	return 0;
 }
 
-LIST_HEAD(yaffsfs_deviceList);
+static LIST_HEAD(yaffsfs_deviceList);
 
 /*
  * yaffsfs_FindDevice