bcachefs: Tweak vfs cache shrinker behaviour

In bcachefs, inodes and dentries are also cached - more compactly - by
the btree node cache, they don't require seeks to recreate.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/fs.c

@@ -1669,6 +1669,8 @@ static struct dentry *bch2_mount(struct file_system_type *fs_type,
 		sb->s_flags	|= SB_POSIXACL;
 #endif
 
+	sb->s_shrink.seeks = 0;
+
 	vinode = bch2_vfs_inode_get(c, BCACHEFS_ROOT_SUBVOL_INUM);
 	if (IS_ERR(vinode)) {
 		bch_err(c, "error mounting: error getting root inode %i",