[why]
For debug purposes we want not to enable DSC on certain connectors
even if algorithm deesires to do so, instead it should enable DSC
on other capable connectors or fail the atomic check.

[how]
Adding the third option to connector's debugfs entry dsc_clock_en.

Accepted inputs:
     0x0 - connector is using default DSC enablement policy
     0x1 - force enable DSC on the connector, if it supports DSC
     0x2 - force disable DSC on the connector, if DSC is supported

Ex. # echo 0x2 > /sys/kernel/debug/dri/0/DP-1/dsc_clock_en
Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>