lightnvm: warn if irqs are disabled in lock laddr

Add a warning if irqs are disabled when locking a new address in rrpc.
The typical path to a new request does not disable irqs, but this is not
guaranteed in the future.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>