cmd/internal/objabi,cmd/link: add support for additional riscv64 relocations

cmd/internal/objabi,cmd/link: add support for additional riscv64 relocations

These additional relocation types are encountered when using the
Go race detector with riscv64.

Updates #64345

Change-Id: I6de6430165fb378463da1af9402198a3a31485ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/690496
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>