f2fs: kill EXT_TREE_VEC_SIZE

Since commit 201ef5e0 ("f2fs: improve shrink performance of extent nodes"),
there is no user of EXT_TREE_VEC_SIZE, just kill it for cleanup.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -519,9 +519,6 @@ enum {
 
 #define MAX_DIR_RA_PAGES	4	/* maximum ra pages of dir */
 
-/* vector size for gang look-up from extent cache that consists of radix tree */
-#define EXT_TREE_VEC_SIZE	64
-
 /* for in-memory extent cache entry */
 #define F2FS_MIN_EXTENT_LEN	64	/* minimum extent length */