R600/SI: Fix suspicious indexing
R600/SI: Fix suspicious indexing

The loop is over the operands of an instruction, and checks the
register with the sub reg index of the dest register. This probably
meant to be checking the sub reg index of the same operand.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@223205 91177308-0d34-0410-b5e6-96231b3b80d8

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