AArch64/ARM64: disentangle the "B.CC" and "LDR lit" operands

These can have different relocations in ELF. In particular both:

    b.eq global
    ldr x0, global

are valid, giving different relocations. The only possible way to distinguish
them is via a different fixup, so the operands had to be separated throughout
the backend.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207105 91177308-0d34-0410-b5e6-96231b3b80d8