[media] tea6415c: return -EIO if i2c_check_functionality fails

If the adapter does not support I2C_FUNC_SMBUS_WRITE_BYTE,
return -EIO instead of 0.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>