docs, bpf: Update command of creating netdevsim
docs, bpf: Update command of creating netdevsim

Since the commit torvalds/linux@e05b2d1 ("netdevsim: move netdev
creation/destruction to dev probe"), the method of adding netdevsim
instance has been changed from using rtnetlink(ip command) to dev probe.

This commit updates command about how to add netdevsim instance.

Signed-off-by: Daniel T. Lee <ecc2a1920afd72449920a2db5c036fd6f80996b7@gmail.com>

tgraf/cilium,cilium-team/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium