go/types, cmd/compile/internal/types2: minor adjustments (cleanups)

go/types, cmd/compile/internal/types2: minor adjustments (cleanups)

go/types:
- gofmt a couple of files

types2:
- add loong64 to sizes list (present in go/types)
- fix a type in validtype.go
- co-locate an accessor with others in typeparam.go

This changes further reduce discrepancy between types2 and go/types.

Change-Id: I2e6a09f1c4b8dbc947c48af13031ff58a2bc6f4d
Reviewed-on: https://go-review.googlesource.com/c/go/+/460996
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>