bcachefs: Fix ec + durability calculation

Durability of an erasure coded pointer doesn't add the device
durability; durability is the same for any extent in that stripe so the
calculation only comes from the stripe.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-11-24 21:52:06 -05:00
commit e4f72bb46a