media: staging: tegra-vde: Do not handle spurious interrupts

Do not handle interrupts if we haven't asked for them, potentially that
could happen if HW wasn't programmed properly.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>