[llvm-readelf]Merge dynamic and static relocation printing to avoid code duplication

The majority of the printRelocation and printDynamicRelocation functions
were identical. This patch factors this all out into a new function.
There are a couple of minor differences to do with printing of symbols
without names, but I think these are harmless, and in some cases a small
improvement.

Reviewed by: grimar, rupprecht, Higuoxing

Differential Revision: https://reviews.llvm.org/D59823

llvm-svn: 357246