We forgot to add the !gccgo tag to cpuid_386.s.

Change-Id: I2de2ed92ac9686c9365cb37cd29121fa98c2bf37
Reviewed-on: https://go-review.googlesource.com/8960Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Ian Lance Taylor <iant@golang.org>