bcachefs fixes for 6.11-rc1

- Fix a typo in the rebalance accounting changes
- BCH_SB_MEMBER_INVALID: small on disk format feature which will be
  needed for full erasure coding support; this is only the minimum so
  that 6.11 can handle future versions without barfing.
-----BEGIN PGP SIGNATURE-----
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=ABhR
-----END PGP SIGNATURE-----