i2c: designware: Rename platform driver probe and PM functions

Make it easier to distinguish between i2c-designware-platdrv and
i2c-designware-core functions and to be consistent with
i2c-designware-pcidrv.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>