[PATCH] fix up CPU detection in p4-clockmod

[PATCH] fix up CPU detection in p4-clockmod

From: Dominik Brodowski <linux@dominikbrodowski.de>

Too many users use the p4-clockmod cpufreq driver instead of the more
advanced speedstep-centrino, speedstep-ich or even acpi drivers.  All of
the latter (usually) provide voltage scaling, while the p4-clockmod driver
only offers a variant of frequency scaling.  So, warn users if they try out
this driver instead.

Also, instead of using a local copy, use the speedstep_lib infrastructure
for detecting the processor speed.  Adding the Pentium-M get_frequency
function to that module only costs about 200 bytes in object size.