i2c: mxc: add CONFIG_CLK support

When CONFIG_CLK enabled, use CLK UCLASS for clk related settings.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>

hs: removed hunk in mxc_i2c_probe() as not longer in code