Revert "drm/amd/display: Remove v_startup workaround for dcn3+"

This reverts commit 3a31e8b8.

We still need to call dcn20_adjust_freesync_v_startup() for older DCN3+
ASICs. Otherwise, it can cause DP to HDMI 2.1 PCONs to fail to light up.

Cc: stable@vger.kernel.org
Link: drm/amd#2809


Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>