CPUFREQ: Mark e_powersaver driver as EXPERIMENTAL and DANGEROUS

The e_powersaver driver for VIA's C7 CPU's needs to be marked as
DANGEROUS as it configures the CPU to power states that are out
of specification.

According to Centaur, all systems with C7 and Nano CPU's support
the ACPI p-state method.  Thus, the acpi-cpufreq driver should
be used instead.

Signed-off-by: Harald Welte <HaraldWelte@viatech.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>