drm/amd/display: Fix DCN 3.01 DSCCLK validation

[why]
DSCCLK validation is not necessary because DSCCLK is derrived from
DISPCLK, therefore if DISPCLK validation passes, DSCCLK is valid, too.
Doing DSCLK validation in addition to DISPCLK leads to modes being
wrongly rejected when DSCCLK was incorrectly set outside of DML.

[how]
Remove DSCCLK validation because it's implicitly validated under DISPCLK

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>