media: ddbridge: fix an error code problem in ddb_probe

[ Upstream commit 09b4195021be69af1e1936cca995712a6d0f2562 ]

Error code is assigned to 'stat', return 'stat' rather than '-1'.

Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>