cmd/compile: adding rule to eliminate ANDCCconst

cmd/compile: adding rule to eliminate ANDCCconst

For example, the Slicemask rule in PPC64 generates a sequence wherein there is andi operation, after an  sradi, which can be replaced by srdi. This new rule eliminates ANDCCconst.

Change-Id: I27aaadf76b9c749a60bcdc5e87b1ebb8167d2fd4
Reviewed-on: https://go-review.googlesource.com/c/go/+/539055
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Jayanth Krishnamurthy <jayanth.krishnamurthy@ibm.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
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