V4L/DVB (3740): Fix oops in budget-av with CI

Now that the CI code reinitialises the frontend, need to move the CI
initialisation to after the frontend init in order to ensure the frontend is
always in a good state. Fixes an oops caused by the frontend being NULL as
well.

Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>