V4L/DVB (6625): CXUSB: i2c transfer failure notification

The i2c master_xfer routine should return a negative result if not all
transfers completed successfully.

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