target-i386: Deconstruct the cpu_T array

All references to cpu_T are done with a constant index.  It aids
readability to decompose the array into two scalar variables.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-Id: <1436426122-12276-11-git-send-email-rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>