f2fs: allocate the extent_cache by default

Let's allocate it to remove the runtime complexity.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 58a91ce..46de782 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -284,8 +284,6 @@ static struct inode *f2fs_new_inode(struct user_namespace *mnt_userns,
 	}
 	F2FS_I(inode)->i_inline_xattr_size = xattr_size;
 
-	f2fs_init_extent_tree(inode, NULL);
-
 	F2FS_I(inode)->i_flags =
 		f2fs_mask_flags(mode, F2FS_I(dir)->i_flags & F2FS_FL_INHERITED);
 
@@ -311,6 +309,8 @@ static struct inode *f2fs_new_inode(struct user_namespace *mnt_userns,
 
 	f2fs_set_inode_flags(inode);
 
+	f2fs_init_extent_tree(inode);
+
 	trace_f2fs_new_inode(inode, 0);
 	return inode;