V4L/DVB (13994): gscpa_stv0680: Fix camera initialization on hotplug

stv0680 cameras currently only work when already plugged in when the system
boots (or when manually re-loading the driver after boot). This patch fixes
this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>