[llvm-objdump,ARM] Make dumpARMELFData line up with instructions.

The whitespace in output lines containing disassembled instructions
was extremely mismatched against that in `.word` lines produced from
dumping literal pools and other data in Arm ELF files. This patch
adjusts `dumpARMELFData` so that it uses the same alignment system as
in the instruction pretty-printers. Now the two classes of line are
aligned sensibly alongside each other.

Reviewed By: DavidSpickett

Differential Revision: https://reviews.llvm.org/D130359