i2c: mxs: Consolidate hard-coded bus address

This patch prepares the MXS I2C driver for the conversion to the
new I2C driver framework by pulling out the hard-coded I2C0 address
from all the places.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Heiko Schocher <hs@denx.de>