cmd/compile: simplify 386's rules
cmd/compile: simplify 386's rules

This CL combines several rules together via regular expression,
but won't impact generated 386 code.

Change-Id: I354006fe801fc952e3a9431cae63229922c9ba48
Reviewed-on: https://go-review.googlesource.com/c/139957
Run-TryBot: Ben Shi <d305faf1f9df9cf68436458fcb54165e72b1642e@163.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

golang/go,CAFxX/go,akutz/go,cloudflare/go,CAFxX/go,josharian/go,golang/go,cloudflare/go,nawawi/go,golang/go,akutz/go,nawawi/go,akutz/go,golang/go,CAFxX/go,josharian/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,josharian/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,cloudflare/go,josharian/go,josharian/go,golang/go,nawawi/go,nawawi/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,cloudflare/go,josharian/go,cloudflare/go,CAFxX/go,CAFxX/go,akutz/go,josharian/go,akutz/go,nawawi/go,cloudflare/go,josharian/go,akutz/go,akutz/go