cmd/compile: don't mark non-generic defined type symbol dupok
For a non-generic defined type, we generate its type descriptor
symbol only in the defining package. So there is no duplicate and
it doesn't need to be dupok.
For unnamed types and instantiated types, the type descriptor can
be generated in multiple packages and so still need to be dupok.
Change-Id: I92ed68c998ad68c5917b77b1dfd62eac4ced6bcf
Reviewed-on: https://go-review.googlesource.com/c/go/+/394636
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>