Edit and clarify comments for TargetInstrInfo methods:
Edit and clarify comments for TargetInstrInfo methods:

None of the existing implementations of commuteInstruction create new
instructions unless the NewMI parameter is true, but the comment had
implied otherwise.

findCommutedOpIndices returns false, not true, when it doesn't know
how to commute the instruction.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@106761 91177308-0d34-0410-b5e6-96231b3b80d8

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