[ Upstream commit 092ff052 ]

free the controller discard_page correctly.

Fixes: cb5b7262 ("nvme: provide fallback for discard alloc failure")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>