i2c: mxc_i2c: Use hex notation for the base address

Printing the I2C controller base address in decimal notation
is not helpful.

Change it to hex notation, which is the standard format found
in the Reference Manual and devicetree.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Acked-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Heiko Schocher <hs@denx.de>