[TargetLowering] Move the setBooleanContents check on (xor (setcc), (setcc)) == ...

[TargetLowering] Move the setBooleanContents check on (xor (setcc), (setcc)) == / != 1 -> (setcc) != / == (setcc) to the right place

We need to be checking the value types for the inner setccs not
the outer setcc. We need to ensure those setccs produce a 0/1
value or that the xor is on the i1 type. I think at the time
this code was originally written, getBooleanContents didn't
take any arguments so this was probably correct. But now we can
have a different boolean contents for integer and floating point.

Not sure why the other combines below the xor were also checking
the boolean contents. None of them involve any setccs other than
the outer one and they only produce a new setcc.

Differential Revision: https://reviews.llvm.org/D69480