bcachefs: btree_root_unreadable_and_scan_found_nothing now AUTOFIX

This will likely mean that the btree had only one node - there was
nothing or almost nothing in it, and we should reconstruct and continue.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/sb-errors_format.h

@@ -290,7 +290,7 @@ enum bch_fsck_flags {
 	x(btree_node_bkey_bad_u64s,				260,	0)		\
 	x(btree_node_topology_empty_interior_node,		261,	0)		\
 	x(btree_ptr_v2_min_key_bad,				262,	0)		\
-	x(btree_root_unreadable_and_scan_found_nothing,		263,	0)		\
+	x(btree_root_unreadable_and_scan_found_nothing,		263,	FSCK_AUTOFIX)	\
 	x(snapshot_node_missing,				264,	0)		\
 	x(dup_backpointer_to_bad_csum_extent,			265,	0)		\
 	x(btree_bitmap_not_marked,				266,	FSCK_AUTOFIX)	\