drm/i2c: tda998x: set the CEC I2C address based on the slave I2C address

The I2C address for the TDA9989 and TDA19989 is fixed at 0x34 but the
two LSBs of the TDA19988's address are set by two configuration pins
on the chip.  Irrespective of the chip, the associated CEC peripheral's
I2C address is based upon the main I2C address.

This patch avoids any special handling required to support systems that
contain multiple TDA19988 devices on the same I2C bus.

Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>