[Why]
Second eDP can send display off notification through HPD
but DC isn't hooked up to handle. Some primary eDP panels
will toggle on/off incorrectly if it's enabled generically.

[How]
Extend the debug option to allow individually enabling hotplug
either the first eDP or the second eDP in a dual eDP system.
Reviewed-by: NNicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: NQingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: NDerek Lai <Derek.Lai@amd.com>
Tested-by: NDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>