axmap: get rid of old debug ->fail_ok checking

Don't assert() on not being able to set a bit. We are returning
the number of bits we set anyway, so just have it return 0.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
parse: fix misparse of bs=64k-128k

We failed parsing the postfix for this case, resulting in
64 and 128k being the result (instead of 64k and 128k).

Signed-off-by: Jens Axboe <axboe@kernel.dk>