drm/amd/display: avoid disable otg when dig was disabled

[Why]
This is a workaround for an dcn3.1 hang that happens if otg dispclk
is ramped while otg is on and stream enc is off.
But this w/a should not trigger when we have a dig active.

[How]
Avoid disable otg when dig was disabled.

Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Jingwen Zhu <Jingwen.Zhu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>