drm/amd/display: HLK Periodic Frame Notification test failed

[Why]
Due to a small pre-fetch window, the active vline timing is a couple
of lines off when compared to what it should be.

[How]
Changed the calculation for the start vline to account for this window.

Signed-off-by: Murton Liu <murton.liu@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c

@@ -150,7 +150,7 @@ void optc1_program_vline_interrupt(
 		req_delta_lines--;
 
 	if (req_delta_lines > vsync_line)
-		start_line = dc_crtc_timing->v_total - (req_delta_lines - vsync_line) - 1;
+		start_line = dc_crtc_timing->v_total - (req_delta_lines - vsync_line) + 2;
 	else
 		start_line = vsync_line - req_delta_lines;