drm/amd/display: Add function for dumping clk registers

[why]
Allow devs to check raw clk register values by dumping them on the log

[how]
Add clk register dump implementation

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Johnson Chen <johnson.chen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>