cpupower: Add support for showing energy performance preference

The EPP value is useful for characterization of performance. Show
it in cpupower frequency-info output.

Link: https://lore.kernel.org/r/20241218191144.3440854-6-superm1@kernel.org


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>