drm/amd/pm: remove duplicate include in 'arcturus_ppt.c'

'amdgpu_dpm.h' included in 'arcturus_ppt.c' is duplicated.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>