i2c-omap: fix am33xx and omap3 fclk_rate

commit f64ed12b accidentally swap fclk_rate from am33xx and omap3.
Revert this change.

Signed-off-by: Jan Weitzel <j.weitzel@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>