Fix the fde encoding used by mips to match gas.

This finally fixes the encoding. The patch also
* Removes eh-frame.ll. It was an unnecessary .ll to .o test that was checking
  the wrong value.
* Merge fde-reloc.s and eh-frame.s into a single test, since the only difference
  was the run lines.
* Don't blindly test the content of the entire .eh_frame section. It makes it
  hard to anyone actually fixing a bug and hitting a difference in a binary
  blob. Instead, use a CHECK for each field and document what is being checked.