trivial: thunderbolt: Don't re-use GErrors
trivial: thunderbolt: Don't re-use GErrors

In instances that we keep processing (such as warnings) these should
be dedicated error variables.

vathpela/fwupd,vathpela/fwupd,hughsie/fwupd,vathpela/fwupd,hughsie/fwupd,vathpela/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd