[ELF2/PPC64] S+A -> R in more places when handling R_PPC64_REL24
[ELF2/PPC64] S+A -> R in more places when handling R_PPC64_REL24

We already have a variable, R, that equals S + A. Use it. NFC.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@250243 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld