[TwoAddressInstruction] Fix ReplacedAllUntiedUses in processTiedPairs

[TwoAddressInstruction] Fix ReplacedAllUntiedUses in processTiedPairs

Fix the calculation of ReplacedAllUntiedUses when any of the tied defs
are early-clobber. The effect of this is to fix the placement of kill
flags on an instruction like this (from @f2 in
 test/CodeGen/SystemZ/asm-18.ll):

  INLINEASM &"stepb $1, $2" [attdialect], $0:[regdef-ec:GRH32Bit], def early-clobber %3:grh32bit, $1:[reguse tiedto:$0], killed %4:grh32bit(tied-def 3), $2:[reguse:GRH32Bit], %4:grh32bit

After TwoAddressInstruction without this patch:

  %3:grh32bit = COPY killed %4:grh32bit
  INLINEASM &"stepb $1, $2" [attdialect], $0:[regdef-ec:GRH32Bit], def early-clobber %3:grh32bit, $1:[reguse tiedto:$0], %3:grh32bit(tied-def 3), $2:[reguse:GRH32Bit], %4:grh32bit

Note that the COPY kills %4, even though there is a later use of %4 in
the INLINEASM. This fails machine verification if you force it to run
after TwoAddressInstruction (currently it is disabled for other
reasons).

After TwoAddressInstruction with this patch:

  %3:grh32bit = COPY %4:grh32bit
  INLINEASM &"stepb $1, $2" [attdialect], $0:[regdef-ec:GRH32Bit], def early-clobber %3:grh32bit, $1:[reguse tiedto:$0], %3:grh32bit(tied-def 3), $2:[reguse:GRH32Bit], %4:grh32bit

Differential Revision: https://reviews.llvm.org/D110848