Remove the code from the scheduler that commuted two-address

instructions to avoid copies, because TwoAddressInstructionPass
also does this optimization.  The scheduler's version didn't
account for live-out values, which resulted in spurious commutes
and missed opportunities.

Now, TwoAddressInstructionPass handles all the opportunities,
instead of just those that the scheduler missed. The result is
usually the same, though there are occasional trivial differences
resulting from the avoidance of spurious commutes.

llvm-svn: 61611