Kconfig: Drop CONFIG_SYS_I2C_DTT_ADDR

This option is only defined to a non-default value by canyonlands, which
needs conversion to driver model (where the I2C address would be defined
by the device tree).

Drop this option.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heiko Schocher <hs@denx.de>