Document the steps to verify the RXE support as prerequisite

[Jeffwan]

In my testing env, I did some test and notice few issues. I would suggest to update the doc and make sure user check the kernel does have the RXE module.

eth0 is not always there, e.g. my test env has ens5. this should be replaced. better to leave a note or make the command more intelligent

root@ip-172-31-16-156:/home/ubuntu/PrisKV# sudo modprobe rdma_rxe 
modprobe: FATAL: Module rdma_rxe not found in directory /lib/modules/6.14.0-1015-aws

I did some additional steps to make it work

sudo apt-get update
sudo apt-get install "linux-modules-extra-$(uname -r)"

root@ip-172-31-16-156:/home/ubuntu/PrisKV# modinfo rdma_rxe | head
filename:       /lib/modules/6.14.0-1015-aws/kernel/drivers/infiniband/sw/rxe/rdma_rxe.ko.zst
alias:          rdma-link-rxe
license:        Dual BSD/GPL
description:    Soft RDMA transport
author:         Bob Pearson, Frank Zago, John Groves, Kamal Heib
srcversion:     56A2147C932A58CF94A16DB
depends:        ib_uverbs,ib_core,udp_tunnel,ip6_udp_tunnel
intree:         Y
name:           rdma_rxe
retpoline:      Y

root@ip-172-31-16-156:/home/ubuntu/PrisKV# rdma link
link rxe_ens5/1 state ACTIVE physical_state LINK_UP netdev ens5