cpufreq/amd-pstate: Change amd_pstate_update_perf() to return an int

As msr_update_perf() calls an MSR it's possible that it fails. Pass
this return code up to the caller.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20241209185248.16301-10-mario.limonciello@amd.com


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>