media: media/test-drivers/Kconfig: fix broken Kconfig

menuconfig DVB_TEST_DRIVERS should be added after the V4L_TEST_DRIVERS,
otherwise there are no drivers listed in these two menus.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 24fb190e ("media: vidtv: implement a tuner driver")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>