Add programming of the DCCG (Display Controller Clock Generator)
block:

HW Blocks:

    +--------+       +--------+
    |  DIO   |       |  DCCG  |
    +--------+       +--------+
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>