This reverts commit r206683.
The code was confusing SEH register numbers with DWARF register numbers.
The test case it was committed with was obviously incorrect. The
disassembler was roundtripping '.seh_pushreg %rsi' as '.seh_pushreg
%rbp', and other exciting things.
Noticed by Vadim Chugunov.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210574 91177308-0d34-0410-b5e6-96231b3b80d8