nvmet: bump NVMET_NR_QUEUES to 128

Raise the max number of IO queues to 128. There are several hosts with
more than 64 cpus/threads.

Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>