cmd/link/internal/loadelf: support additional ELF relocations on mips64
cmd/link/internal/loadelf: support additional ELF relocations on mips64

LLVM on openbsd/mips64 generates R_MIPS_GOT_HI16 and R_MIPS_GOT_LO16 relocations,
so teach cmd/link/internal/loadelf about both of these.

Updates #43005

Change-Id: Ic45ea8b901d44dcbdbf355411ee434dcd7670a92
Reviewed-on: https://go-review.googlesource.com/c/go/+/275894
Trust: Joel Sing <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@sing.id.au>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

cloudflare/go,nawawi/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,golang/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,CAFxX/go,golang/go,golang/go,nawawi/go,nawawi/go,CAFxX/go,golang/go,CAFxX/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go