drm/amd/display: Skip to enable dsc if it has been off

[Why]
It makes DSC enable when we commit the stream which need
keep power off.And then it will skip to disable DSC if
pipe reset at this situation as power has been off. It may
cause the DSC unexpected enable on the pipe with the
next new stream which doesn't support DSC.

[HOW]
Check the DSC used on current pipe status when update stream.
Skip to enable if it has been off. The operation enable
DSC should happen when set power on.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Paul Hsieh <Paul.Hsieh@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>