block: mark bdev files as FMODE_NOWAIT if underlying device supports it

We set this unconditionally, but it really should be dependent on if
the underlying device is nowait compliant.

Cc: linux-block@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230509151910.183637-3-axboe@kernel.dk


Signed-off-by: Jens Axboe <axboe@kernel.dk>