[ELF] - Convert overlapping-sections.s testcase to x86 and cleanup.

Patch do the following changes:

* Test case was converted from MIPS to x86.

* Removed part of the test checking we are able to produce a valid output.
  Since we do that already in other tests, this one's intention should be
  only to check we are still able to report overlaps and/or produce
  broken output with overlaps.

Differential revision: https://reviews.llvm.org/D44438

llvm-svn: 327480