bcachefs: fix eytzinger0_find_gt()

- fix return types: promoting from unsigned to ssize_t does not do what
we want here, and was pointless since the rest of the eytzinger code
is u32
- nr, not size

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

bcachefs: Etyzinger cleanups

Pull out eytzinger.c and kill eytzinger_cmp_fn. We now provide
eytzinger0_sort and eytzinger0_sort_r, which use the standard cmp_func_t
and cmp_r_func_t callbacks.

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

bcachefs: eytzinger_for_each() declares loop iter

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

bcachefs: eytzinger0_find() search should be const

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

bcachefs: Make eytzinger size parameter more conventional

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

bcachefs: Fix check for if extent update is allocating

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

bcachefs: Initial commit

Initially forked from drivers/md/bcache, bcachefs is a new copy-on-write
filesystem with every feature you could possibly want.

Website: https://bcachefs.org

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