[Why]
During S4/S3 stress test it is possible to resume from S4 without
calling mode set on eDP, meaning high level optimization flag is not
reset. If this is followed by an S3 resume call, driver will see
optimization flag is set and consume it and think backend is powered
on when in fact it is not.

This results in PHY being off in sequence where
S4->Resume->S3->Resume->ApplyOpt->black screen.

[How]
Move optimization flag to stream instead of a DC flag.
Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>