drm/amd/display: Add dual edp optimization flag.

[Why & How]
Add a dual edp power optimization flag, so driver will
notify this flag to dmub FW to determine if apply the
power optimization.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Bindu Ramamurthy <bindu.r@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>