go/types: don't report cycle error if clearer error follows

go/types: don't report cycle error if clearer error follows

If a cyclic declaration uses a non-type object where it expects
a type, don't report the cycle error in favor of the clearer and
more informative error about the missing type.

Fixes #25790.

Change-Id: If937078383def878efb4c69686e5b4b2a495fd5d
Reviewed-on: https://go-review.googlesource.com/135700
Reviewed-by: Alan Donovan <adonovan@google.com>