lightnvm: do not load L2P table if not supported

An Open-Channel SSD can work on two modes: (i) hybrid mode, where the
L2P table is maintained both by the host and by the device; and (ii)
full host-based, where the L2P table is uniquely maintained by the host.

In the advent of a new target implementing the full host-based mode, do
not assume that the L2P table must be loaded on the generic media
manager; check device properties loaded on the identify command instead.

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