Since none of the code in the LNetPut/send path really uses LNET_MAX_PAYLOAD but they do check LNET_MAX_IOV, remove the restriction on LNET_MAX_PAYLOAD to be PAGE_SIZE * LNET_MAX_IOV.

This allows us to build Lustre with a configure flag of --max-payload-mb=XXX. This enables Cray DVS to send larger requests through the network, greatly reducing the software overhead.

There are more discussions in Oracle Bug 22293.