nvme: always initialize known command effects

Instead of appending command effects flags per IO, set the known effects
flags the driver needs to react to just once during initial setup.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>