[media] tm6000: Execute lightweight reset on close

When the last user closes the device, perform a lightweight reset of the
device to bring it into a well-known state.

Note that this is not always enough with the TM6010, which sometimes
needs a hard reset to get into a working state again.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>