cpufreq/amd-pstate: Refactor amd_pstate_epp_reenable() and amd_pstate_epp_offline()

Replace similar code chunks with amd_pstate_update_perf() and
amd_pstate_set_epp() function calls.

Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20241204144842.164178-4-Dhananjay.Ugwekar@amd.com


[ML: Fix LKP reported error about unused variable]
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>