[CPUFREQ] p4-clockmod: reduce noise

On those CPUs which are SpeedStep (EST) capable, we do not care at all if
p4-clockmod does not work, since a technically superior CPU frequency
management technology is to be used.

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