i965/compaction: Remove unnecessary is-compacted? check.
i965/compaction: Remove unnecessary is-compacted? check.

Used to pass over previously compacted instructions in this loop, but no
longer. No point in checking.

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

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