drm/tegra: dc: Fix reference leak in tegra_dc_couple()

driver_find_device() calls get_device() to increment the reference
count once a matching device is found, but there is no put_device() to
balance the reference count. To avoid reference count leakage, add
put_device() to decrease the reference count.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: a31500fe70 ("drm/tegra: dc: Restore coupling of display controllers")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Acked-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patch.msgid.link/20251022114720.24937-1-make24@iscas.ac.cn

drivers/gpu/drm/tegra/dc.c

@@ -3148,6 +3148,7 @@ static int tegra_dc_couple(struct tegra_dc *dc)
 		dc->client.parent = &parent->client;
 
 		dev_dbg(dc->dev, "coupled to %s\n", dev_name(companion));
+		put_device(companion);
 	}
 
 	return 0;