Add support to program the HUBBUB (DCN memory HUB interface)

HW Blocks:

 +--------+
 | HUBBUB |
 +--------+
        |
        v
    +--------+
    |  DPP   |
    +--------+
        |
        v
    +--------+
    |  MPC   |
    +--------+
        |
        v
    +-------+
    |  OPP  |
    +-------+
        |
        v
    +--------+
    |  OPTC  |
    +--------+
        |
        v
    +--------+       +--------+
    |  DIO   |       |  DCCG  |
    +--------+       +--------+
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>