cmd/compile: simplify mkinlcall1
cmd/compile: simplify mkinlcall1

mkinlcall1 already guards against recursively inlining functions into
themselves, so there's no need to clear and restore fn.Func.Inl during
recursive inlining.

Passes toolstash-check.

Change-Id: I8bf0c8dea8788d94d3ea5670610b4acb1d26d2fb
Reviewed-on: https://go-review.googlesource.com/69310
Run-TryBot: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

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