[SystemZ] Refactor some VT casts in DAG match patterns
[SystemZ] Refactor some VT casts in DAG match patterns

In patterns where we need to specify a result VT, prefer

  [(set (tr.vt tr.op:$V1), (operator ...))]

over

  [(set tr.op:$V1, (tr.vt (operator ...)))]

This is NFC now, but simplifies some future changes.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@331192 91177308-0d34-0410-b5e6-96231b3b80d8

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