Add fnv hash

Signed-off-by: Jens Axboe <axboe@fb.com>
crc/test: add fnv

Signed-off-by: Jens Axboe <axboe@fb.com>
bloom: up hashes to 5 by default

Signed-off-by: Jens Axboe <axboe@fb.com>
t/dedupe: fixup bloom entry calculation

With m/n at 8x and with 5 default hashes for blooming, we should
be around ~2% false positive rate max.

Signed-off-by: Jens Axboe <axboe@fb.com>