V4L/DVB (6628): zl10353: Improve support for boards without a tuner on secondary i2c

Issue FSM_GO instead of TUNER_GO if there is no tuner attached to the
secondary i2c bus.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>