Object: add type names for ARM/COFF relocations

Add type name mappings for the ARM COFF relocations.  This allows for objdump to
provide a more useful description of relocations in disassembly inline form.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205834 91177308-0d34-0410-b5e6-96231b3b80d8