[media] m5mols: Fix typo in get_fmt callback

The check of return value from __find_format() was inverted
by mistake. This patch fixes regression introduced in commit
5565a2ad47 [media] m5mols: Protect driver data with a mutex

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>