nvme: remove the ifdef around nvme_nvm_ioctl

[ Upstream commit 3f98bcc58cd5f1e4668db289dcab771874cc0920 ]

We already have a proper stub if lightnvm is not enabled, so don't bother
with the ifdef.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>