[ELF] Remove redundant conversion of section content from ArrayRef to
StringRef before calling the createSectionAtom() method and reverse
conversion inside the method.

No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206022 91177308-0d34-0410-b5e6-96231b3b80d8
[Mips] Factor out MIPS relocation addend reading to the separate
function.

No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206023 91177308-0d34-0410-b5e6-96231b3b80d8