Remove dead code.

MO_JumpTableIndex and MO_ExternalSymbol don't show up on inline asm.

Keeping parts of the old asm printer just to print inline asm to a string that
we then parse back looks like a hack.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196111 91177308-0d34-0410-b5e6-96231b3b80d8