drm/amdgpu/smu11: add support for SMU AC/DC interrupts

Driver needs to send the ack message when it receives the
AC/DC interrupt from the SMU.

TODO: verify the client and src ids.

Bug: https://gitlab.freedesktop.org/drm/amd/issues/1043


Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>