Add support for AMD MPERF/APERF

Add support for AMD MPERF/APERF

Starting with Family 0x10, model 10 processors, some AMD processors
will have support for the APERF/MPERF MSRs.  This patch adds the
checks necessary to support those MSRs.

It also makes the get_measured_perf function defined inside cpufreq.c
driver independent.  max_freq is taken from the policy definition
instead of being a private argument in struct acpi_cpufreq_data.
The struct member is entirely removed from the function since it
is no longer used.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>