cpu-o3: Fix "OldestReady" scheduling bug
cpu-o3: Fix "OldestReady" scheduling bug

Fixed a bug in the SMT scheduling function oldestReady(), where
the oldest sequence number and its thread id were mixed up.

Change-Id: I31df5eac73ecabbe04fb54624ee1b1867fa4d3c0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/46940
Reviewed-by: Richard Cooper <5451b9f082a6f419264dc2e8898d5200257ca9ce@arm.com>
Reviewed-by: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Maintainer: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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