drm/amd/display: Remove unused panel patch "disconnect_delay"

[Why]
This patch is for use by dm, no need for it in dc.

Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>