Revert "drm/amd/display: disable dcn20 abm feature for bring up"

This reverts commit 96cb7cf1.

This change was used for DCN2 bringup and is no longer desired.
In fact it breaks backlight on DCN2 systems.

Cc: Alexander Monakov <amonakov@ispras.ru>
Cc: Hersen Wu <hersenxs.wu@amd.com>
Cc: Anthony Koo <Anthony.Koo@amd.com>
Cc: Michael Chiu <Michael.Chiu@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reported-and-tested-by: Alexander Monakov <amonakov@ispras.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -1356,7 +1356,7 @@ static int dm_late_init(void *handle)
 	unsigned int linear_lut[16];
 	int i;
 	struct dmcu *dmcu = NULL;
-	bool ret = false;
+	bool ret;
 
 	if (!adev->dm.fw_dmcu)
 		return detect_mst_link_for_all_connectors(adev->ddev);
@@ -1377,13 +1377,10 @@ static int dm_late_init(void *handle)
 	 */
 	params.min_abm_backlight = 0x28F;
 
-	/* todo will enable for navi10 */
-	if (adev->asic_type <= CHIP_RAVEN) {
 	ret = dmcu_load_iram(dmcu, params);
 
 	if (!ret)
 		return -EINVAL;
-	}
 
 	return detect_mst_link_for_all_connectors(adev->ddev);
 }