drm/tegra: dsi: detect possible_crtcs

Other platforms allow dsi across multiple heads, but some have
one or more heads disabled. This results in a mismatch between
possible_crtcs and the real crtc mask. Apply the same
`tegra_output_find_possible_crtcs` function to DSI to properly
detect.

drivers/gpu/drm/tegra/dsi.c

@@ -1088,7 +1088,7 @@ static int tegra_dsi_init(struct host1x_client *client)
 			dev_err(dsi->dev, "failed to initialize output: %d\n",
 				err);
 
-		dsi->output.encoder.possible_crtcs = 0x3;
+		tegra_output_find_possible_crtcs(&dsi->output, drm);
 	}
 
 	return 0;