yaffs: Remove private list implementation

U-Boot already has a list implementation, and files which include both
that and the yaffs implementation will get errors:

In file included from ydirectenv.h:80:0,
                 from yportenv.h:81,
                 from yaffs_guts.h:19,
                 from yaffs_allocator.h:19,
                 from yaffs_allocator.c:14:
yaffs_list.h:32:8: error: redefinition of ‘struct list_head’
 struct list_head {
        ^

Remove the yaffs implementation.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/fs/yaffs2/ydirectenv.h b/fs/yaffs2/ydirectenv.h
index c2ffbfd..c6614f1 100644
--- a/fs/yaffs2/ydirectenv.h
+++ b/fs/yaffs2/ydirectenv.h
@@ -77,7 +77,7 @@
 #define YAFFS_ROOT_MODE			0666
 #define YAFFS_LOSTNFOUND_MODE		0666
 
-#include "yaffs_list.h"
+#include "linux/list.h"
 
 #include "yaffsfs.h"