cpufreq/amd-pstate: Convert the amd_pstate_get/set_epp() to static calls

cpufreq/amd-pstate: Convert the amd_pstate_get/set_epp() to static calls

MSR and shared memory based systems have different mechanisms to get and
set the epp value. Split those mechanisms into different functions and
assign them appropriately to the static calls at boot time. This eliminates
the need for the "if(cpu_feature_enabled(X86_FEATURE_CPPC))" checks at
runtime.

Also, propagate the error code from rdmsrl_on_cpu() and cppc_get_epp_perf()
to *_get_epp()'s caller, instead of returning -EIO unconditionally.

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/20241204144842.164178-2-Dhananjay.Ugwekar@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>