designware_i2c: Enhance DesignWare I2C driver address support

Enhance the DesignWare I2C driver to support address length more
than 1 byte. This enhancement is required as some I2C slave
device such as EEPROM chip might have 16 bit address byte.

Signed-off-by: Chin Liang See <clsee@altera.com>
Acked-by: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: Tom Rini <trini@ti.com>
cc: Armando Visconti <armando.visconti@st.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Heiko Schocher <hs@denx.de>