riscv64*: enable OFED

Summary:
OFED on riscv64 builds fine, so it's ok to enable it.

Also MFC to stable/13.

Test Plan: make buildworld

Reviewers: mhorne

Subscribers: bdrewery, imp, emaste

Differential Revision: https://reviews.freebsd.org/D33602

(cherry picked from commit 40218ffe8c85118a2bab0eb8c7bc3525d4ad639e)