CPUFREQ: Enable acpi-cpufreq driver for VIA/Centaur CPUs

The VIA/Centaur C7, C7-M and Nano CPU's all support ACPI based cpu p-states
using a MSR interface.  The Linux driver just never made use of it, since in
addition to the check for the EST flag it also checked if the vendor is Intel.

Signed-off-by: Harald Welte <HaraldWelte@viatech.com>
[ Removed the vendor checks entirely  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>