lightnvm: fix request intersection locking in rrpc

This patch fixes an error on the calculation of intersecting logical
addresses; it contemplates the case where a new request including
several addresses intersects with a single locked address. This case is
typical when multiple pages are sent in a new request, while GC - which
at the moment sends one address at the time - is running.

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