x86: Add #ifdef CONFIG_COMPAT to <asm/sys_ia32.h>

Unfortunately a lot of the compat types are guarded with CONFIG_COMPAT
or the equivalent, so add a similar guard to <asm/sys_ia32.h> to avoid
compilation failures when CONFIG_COMPAT=n.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>