i2c: designware: move #ifdef CONFIG_OF to the top

Move the #ifdef CONFIG_OF section to the top of the file, after the ACPI
section so functions defined there can be used in dw_i2c_plat_probe.

Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>