cpufreq/amd-pstate: Drop actions in amd_pstate_epp_cpu_offline()

When the CPU goes offline there is no need to change the CPPC request
because the CPU will go into the deepest C-state it supports already.

Actually changing the CPPC request when it goes offline messes up the
cached values and can lead to the wrong values being restored when
it comes back.

Instead drop the actions and if the CPU comes back online let
amd_pstate_epp_set_policy() restore it to expected values.

Reviewed-by: Dhananjay Ugwekar <dhananjay.ugwekar@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>