nvme: Don't hardcode the data len for pr commands

Reservation Report support needs to pass in a variable sized buffer, so
this patch has the pr command helpers take a data length argument.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230407200551.12660-9-michael.christie@oracle.com


Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>