[dev.regabi] cmd/compile: remove a couple CloneName calls

In inl.go, that code path is unused, since we added ir.BasicLit to
represent unnamed OLITERALs.

In race.go, rather than cloning ir.RegFP, we can just create it from
scratch again.

Passes toolstash -cmp (incl. w/ -race).

Change-Id: I8e063e4898d2acf056ceca5bc03df6b40a14eca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/281192


Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>