drm/amd/display: Revert "Guard ASSR with internal display flag"

This reverts commit 9127daa0.

[Why]
1. Previous patch regresses on some embedded panels.
2. Project coreboot doesn't support passing of internal display flag.

[How]
This reverts "Guard ASSR with internal display flag" commit.

Fixes: 9127daa0 ("drm/amd/display: Guard ASSR with internal display flag")
Bug: drm/amd#1620


Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Reviewed-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Acked-by: Bindu Ramamurthy <bindu.r@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org