V4L/DVB: ngene: Fix I2C initialisation

Use I2C_CLASS_TV_DIGITAL, not I2C_ADAP_CLASS_TV_DIGITAL.
Remove initialisation of bus_lock mutex.
Thanks to Mauro for pointing out.

Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Thanks-to: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>