[llvm-readobj/llvm-readelf] - Remove gnu-relocations.test completely.

rL362089 introduced a set of yaml based reloc-types-*.test test cases
(instead of huge reloc-types.test that used a lot of precompiled binaries)
These test cases checks LLVM-styled dumping of the relocations.

gnu-relocations.test was a test case to check GNU styled relocations dumping.
It did that only for elf-x86 and elf-x86_64 targets. It did not test all of the
relocations though.

Now, after rL362089, it does not make sence to keep it.
This patch updates reloc-types-elf-i386.test and reloc-types-elf-x64.test tests
with llvm-readelf calls to check GNU styled output in one place.
It removes gnu-relocations.test completely.

One of intentions of doing this is also to get rid of relocs.obj.elf-i386 and
relocs.obj.elf-x86_64 precompiled objects completely (they are used in other tests still).

Differential revision: https://reviews.llvm.org/D62655

llvm-svn: 362374