x86: Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS

x86: Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS

Allow dom0 to write MSR IA32_ENERGY_PERF_BIAS

There is a new hardware feature, which lets system software to set
Energy Performance Preference. This is a opaque knob in the form of
IA32_ENERGY_PERF_BIAS MSR, which has a 4 bit Energy Performance
Preference Hint.

The support for this feature is indicated by CPUID.06H.ECX.bit3. Refer
to Intel Architectures Software Developer's Manual for more info.

Let dom0 tools to control it.

Signed-off-by: Wei Gang <gang.wei@intel.com>