nvme: cleanup double shift issue

The problem here is that set_bit() and test_bit() take a bit number so
we should be passing 0 but instead we're passing (1 << 0) which leads to
a double shift.  It doesn't cause a runtime bug in the current code
because it's done consistently and we only set that one bit.

I decided to just re-use NVME_AER_NOTICE_NS_CHANGED instead of
introducing a new define for this.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>