nvme: clear caller pointer on identify failure

[ Upstream commit 7e80eb79 ]

The memory allocated for the identification is freed on failure. Set
it to NULL so the caller doesn't have a pointer to that freed address.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>