[release-branch.go1.21] cmd/compile: don't combine loads in generated equality functions
... if the architecture can't do unaligned loads.
We already handle this in a few places, but this particular place
was added in CL 399542 and missed this additional restriction.
Fixes #67164
(Reroll of CL 583303)
Change-Id: Id067cc2e39d7d199672f2017f7f53991fb23f8d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/583799
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Keith Randall <khr@golang.org>