drm/amd/pm: correct Arcturus mmTHM_BACO_CNTL register address

Arcturus has a different register address from other SMU V11
ASICs.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>