designware_i2c: disable i2c controller during target address setup

designware_i2c: disable i2c controller during target address setup

As it is stated in DesignWare I2C databook: writes to IC_TAR (0x4)
register succeed only when IC_ENABLE[0] is set to 0.

Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Tom Rini <[email protected]>
cc: Armando Visconti <[email protected]>
Cc: Stefan Roese <[email protected]>
Cc: Albert ARIBAUD <[email protected]>
Cc: Heiko Schocher <[email protected]>
Cc: Vipin KUMAR <[email protected]>
Cc: Tom Rix <[email protected]>
Cc: Mischa Jonker <[email protected]>