nvme: fix incorrect behavior when BLKROSET is called by the user

The offending commit breaks BLKROSET ioctl because a device
revalidation will blindly override BLKROSET setting. Hence,
we remove the disk rw setting in case NVME_NS_ATTR_RO is cleared
from by the controller.

Fixes: 1293477f ("nvme: set gendisk read only based on nsattr")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>