Revert "r306529 - [X86] Correct dwarf unwind information in function epilogue"

I am 99% sure that this breaks the PPC ASAN build bot:
http://lab.llvm.org:8011/builders/sanitizer-ppc64be-linux/builds/3112/steps/64-bit%20check-asan/logs/stdio

If it doesn't go back to green, we can recommit (and fix the original
commit message at the same time :) ).

llvm-svn: 306676