platform/x86: amd-pmc: Output error codes in messages

The return type for the s2idle callbacks is 'void', so any errors that
occur will no longer be displayed.

Output these error codes in the messages in case of any failures.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20220317141445.6498-3-mario.limonciello@amd.com


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>