scsi: lpfc: Fix nvmet RQ resource needs for large block writes.

Large block writes to the nvme target were failing because the default
number of RQs posted was insufficient.

Expand the NVMET RQs to 2048 RQEs and ensure a minimum of 512 RQEs are
posted, no matter how many MRQs are configured.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>