cmd/compile/internal/types: remove IterFields
cmd/compile/internal/types: remove IterFields

No longer needed after previous CLs.

Change-Id: I9dd1040f3f28363c44434a810cbd7061cf6a028f
Reviewed-on: https://go-review.googlesource.com/39857
Run-TryBot: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Dave Cheney <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@cheney.net>
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

cloudflare/go,christopher-henderson/Go,CAFxX/go,nawawi/go,golang/go,derekmarcotte/go,akutz/go,ImJasonH/go,nawawi/go,josharian/go,golang/go,josharian/go,josharian/go,ImJasonH/go,vsekhar/elastic-go,ImJasonH/go,codestation/go,Cofyc/go,polyverse-security/go,cloudflare/go,vsekhar/elastic-go,vsekhar/elastic-go,nawawi/go,akutz/go,vsekhar/elastic-go,cloudflare/go,ImJasonH/go,akutz/go,codestation/go,ImJasonH/go,ImJasonH/go,CAFxX/go,nawawi/go,golang/go,polyverse-security/go,Cofyc/go,derekmarcotte/go,cloudflare/go,josharian/go,josharian/go,codestation/go,codestation/go,akutz/go,Cofyc/go,Cofyc/go,vsekhar/elastic-go,josharian/go,CAFxX/go,codestation/go,nawawi/go,CAFxX/go,golang/go,polyverse-security/go,ImJasonH/go,vsekhar/elastic-go,derekmarcotte/go,polyverse-security/go,cloudflare/go,Cofyc/go,polyverse-security/go,nawawi/go,josharian/go,CAFxX/go,ImJasonH/go,cloudflare/go,derekmarcotte/go,CAFxX/go,nawawi/go,golang/go,vsekhar/elastic-go,josharian/go,codestation/go,Cofyc/go,codestation/go,derekmarcotte/go,CAFxX/go,nawawi/go,CAFxX/go,akutz/go,codestation/go,cloudflare/go,akutz/go,derekmarcotte/go,derekmarcotte/go,derekmarcotte/go,cloudflare/go,Cofyc/go,Cofyc/go,polyverse-security/go,golang/go,golang/go,golang/go,akutz/go,polyverse-security/go,akutz/go,vsekhar/elastic-go,polyverse-security/go