drm/amd/powerplay: add lock protection for swSMU APIs V2

This is a quick and low risk fix. Those APIs which
are exposed to other IPs or to support sysfs/hwmon
interfaces or DAL will have lock protection. Meanwhile
no lock protection is enforced for swSMU internal used
APIs. Future optimization is needed.

V2: strip the lock protection for all swSMU internal APIs

Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Feifei Xu <Feifei.Xu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>