platform/x86/amd: pmc: Use pm_pr_dbg() for suspend related messages

Using pm_pr_dbg() allows users to toggle `/sys/power/pm_debug_messages`
as a single knob to turn on messages that amd-pmc can emit to aid in
any s2idle debugging.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>