[media] cx231xx: disable I2C errors during i2c_scan

Otherwise, it would produce lots of useless messages like:
	cx231xx: cx231xx_send_usb_command: failed with status --32

After this patch, I2C scan will produce an useful report:

[ 9494.050807] cx231xx: i2c_scan: checking for I2C devices on port=0 ..
[ 9494.074928] cx231xx: i2c scan: Completed Checking for I2C devices on port=0.
[ 9494.074936] cx231xx: i2c_scan: checking for I2C devices on port=3 ..
[ 9494.098934] cx231xx: i2c scan: Completed Checking for I2C devices on port=3.
[ 9494.098942] cx231xx: i2c_scan: checking for I2C devices on port=2 ..
[ 9494.118440] cx231xx: i2c scan: Completed Checking for I2C devices on port=2.
[ 9494.118448] cx231xx: i2c_scan: checking for I2C devices on port=4 ..
[ 9494.141889] cx231xx: i2c scan: Completed Checking for I2C devices on port=4.

[ 9494.060182] cx231xx: i2c scan: found device @ 0x40  [???]
[ 9494.062953] cx231xx: i2c scan: found device @ 0x60  [colibri]
[ 9494.066071] cx231xx: i2c scan: found device @ 0x88  [hammerhead]
[ 9494.067383] cx231xx: i2c scan: found device @ 0x98  [???]
[ 9494.090113] cx231xx: i2c scan: found device @ 0xa0  [eeprom]
[ 9494.106463] cx231xx: i2c scan: found device @ 0x60  [colibri]
[ 9494.113762] cx231xx: i2c scan: found device @ 0xc0  [tuner]
[ 9494.121882] cx231xx: i2c scan: found device @ 0x20  [???]
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>