[MachineSinking] Clear kill flag of all operands at all their uses.

When sinking an instruction it might be moved past the original last use of one
of its operands. This last use has the kill flag set and the verifier will
obviously complain about this.

Before Machine Sinking (AArch64):
%vreg3<def> = ASRVXr %vreg1, %vreg2<kill>
%XZR<def> = SUBSXrs %vreg4, %vreg1<kill>, 160, %NZCV<imp-def>
...

After Machine Sinking:
%XZR<def> = SUBSXrs %vreg4, %vreg1<kill>, 160, %NZCV<imp-def>
...
%vreg3<def> = ASRVXr %vreg1, %vreg2<kill>

This fix clears all the kill flags in all instruction that use the same operands
as the instruction that is being sunk.

This fixes rdar://problem/18180996.

llvm-svn: 216803