nvme-multipath: drop optimization for static ANA group IDs

[ Upstream commit 78a61cd42a64f3587862b372a79e1d6aaf131fd7 ]

Bit 6 in the ANACAP field is used to indicate that the ANA group ID
doesn't change while the namespace is attached to the controller.
There is an optimisation in the code to only allocate space
for the ANA group header, as the namespace list won't change and
hence would not need to be refreshed.
However, this optimisation was never carried over to the actual
workflow, which always assumes that the buffer is large enough
to hold the ANA header _and_ the namespace list.
So drop this optimisation and always allocate enough space.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>