drm/amd/display: Fix incorrect dsc force enable logic

[Why]
Missed removing a '!' which results in incorrect behavior

[How]
Remove the offending '!'

Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201015194053.355335-1-eryk.brol@amd.com