drm/amdgpu: move smu_debug_mask to a more proper place

As the smu_context will be invisible from outside(of power). Also,
the smu_debug_mask can be shared around all power code instead of
some specific framework(swSMU) only.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>