block/nvme: Use definitions instead of magic values in add_io_queue()

block/nvme: Use definitions instead of magic values in add_io_queue()

Replace magic values by definitions, and simplifiy since the
number of queues will never reach 64K.

Reviewed-by: Eric Auger <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Tested-by: Eric Auger <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Message-id: 20201029093306.1063879[email protected]
Signed-off-by: Stefan Hajnoczi <[email protected]>
Tested-by: Eric Auger <[email protected]>