[PECOFF] Fix AMD64_ADDR64 relocation.

IMAGE_REL_AMD64_ADDR64 relocation should set 64-bit *VA* (virtual
address) instead of *RVA* (relative virtual address), so we have
to add the iamge base to the target's RVA.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@216512 91177308-0d34-0410-b5e6-96231b3b80d8