drm/amd/display: Limit NV12 chroma workaround

[Why]
It is causing green Line at the bottom of SDR 480p
MPO playback

[How]
Limit workaround to vertical > 512
Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@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/dcn21/dcn21_hubp.c

@@ -200,7 +200,7 @@ void hubp21_set_viewport(
 	 *	Disable w/a when rotated 180 degrees, causes vertical chroma offset
 	 */
 	patched_viewport_height = viewport_c->height;
-	if (viewport_c->height != 0 && debug->nv12_iflip_vm_wa &&
+	if (debug->nv12_iflip_vm_wa && viewport_c->height > 512 &&
 			rotation != ROTATION_ANGLE_180) {
 		int pte_row_height = 0;
 		int pte_rows = 0;