drm/amd/display: Various logs added

[Why & How]
Added logs for panel delays, spread_spectrum_percentage,
and gpuclk_ss_percentage to facilitate debugging.

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