It is useful information in dmesg to have a message indicating that the i2c
driver was succesfully registered, so promote it to dev_info.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>