[media] em28xx: Fix memory leak on driver defered resource release

When the device is physically unplugged but there are still
open file handles, resource release is defered until last
opened handle is closed.
This patch fixes a missing em28xx_fh struct release.
Tested by compilation only.

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>