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 FE/BE FIFO was not switched.

Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@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>