[CPUFREQ] p4-clockmod: add more CPUs

Several more Intel CPUs are now capable using the p4-clockmod cpufreq
driver. As it is of limited use most of the time, print a big bold warning
if a better cpufreq driver might be available.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Dave Jones <davej@redhat.com>