drm/amd/display: Keep eDP stream enabled during boot.

This path fixed specific eDP panel cold boot black screen
due to unnecessary enable link.
Change:
In case of boot up with eDP, if OS is going to set mode
on eDP, keep eDP light up, do not disable and reset corresponding
HW.
This change may affect dce asics and S3/S4 Resume with multi-monitor.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>