bcachefs: Add an .invalid method for bch2_btree_ptr_v2

It was using the method for btree_ptr_v1, but that wasn't checking all
the fields.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2 files changed