omap-i2c: fix incorrect log message when using a device tree

When booting using a device tree, the adapter number is dynamically
assigned after the log message is sent.
This patch modifies the log message to get a correct adapter id.

Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Tested-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>