V4L/DVB: radio_timberdale: depends on I2c

RADIO_TIMBERDALE selects RADIO_SAA7706H, but RADIO_SAA7706H
depends on I2C, so make RADIO_TIMBERDALE depend on I2C also;
otherwise there are build errors:

drivers/media/radio/saa7706h.c:139: error: implicit declaration of function 'i2c_master_send'
drivers/media/radio/saa7706h.c:148: error: implicit declaration of function 'i2c_transfer'
drivers/media/radio/saa7706h.c:372: error: implicit declaration of function 'i2c_check_functionality'
drivers/media/radio/saa7706h.c:375: error: implicit declaration of function 'i2c_adapter_id'
drivers/media/radio/saa7706h.c:438: error: implicit declaration of function 'i2c_add_driver'
drivers/media/radio/saa7706h.c:443: error: implicit declaration of function 'i2c_del_driver'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Mocean Laboratories <info@mocean-labs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>