nvme: Increase block size variable size to 32-bit

Increase block size variable size to 32-bit unsigned to be able to
support block devices larger than 32k (starting from 64 KiB).

Physical and logical block size already support unsigned 32-bit.

Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>