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 <joel@sing.id.au>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/link/internal/loadelf/ldelf.go

@@ -969,13 +969,17 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
 	case MIPS | uint32(elf.R_MIPS_HI16)<<16,
 		MIPS | uint32(elf.R_MIPS_LO16)<<16,
 		MIPS | uint32(elf.R_MIPS_GOT16)<<16,
+		MIPS | uint32(elf.R_MIPS_GOT_HI16)<<16,
+		MIPS | uint32(elf.R_MIPS_GOT_LO16)<<16,
 		MIPS | uint32(elf.R_MIPS_GPREL16)<<16,
 		MIPS | uint32(elf.R_MIPS_GOT_PAGE)<<16,
 		MIPS | uint32(elf.R_MIPS_JALR)<<16,
 		MIPS | uint32(elf.R_MIPS_GOT_OFST)<<16,
 		MIPS64 | uint32(elf.R_MIPS_HI16)<<16,
 		MIPS64 | uint32(elf.R_MIPS_LO16)<<16,
 		MIPS64 | uint32(elf.R_MIPS_GOT16)<<16,
+		MIPS64 | uint32(elf.R_MIPS_GOT_HI16)<<16,
+		MIPS64 | uint32(elf.R_MIPS_GOT_LO16)<<16,
 		MIPS64 | uint32(elf.R_MIPS_GPREL16)<<16,
 		MIPS64 | uint32(elf.R_MIPS_GOT_PAGE)<<16,
 		MIPS64 | uint32(elf.R_MIPS_JALR)<<16,