add registers for dcn, clk, and renoir ip offsets

v2: header cleanup (Alex)
v3: Add DPCS registers (Hersen)
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>