prov/efa: Rework zcpy recv setting

[shijin-aws]

This patch refactor the efa_rdm_ep_set_use_zcpy_rx function for better readability and logging. It also removes the requirement for FI_MSG_PREFIX

[shijin-aws]

Good change. Let's use e.g. "Zero-copy receive protocol" over "zcpy rx" for logging, documentation, etc.

Also, we seem to be missing documentation for FI_EFA_USE_ZCPY_RX in fi_efa(7)

Good point, updated in the latest revision

[shijin-aws]

Just nits

Thank you ! Updated all