i2c: pxa: remove incorrect __exit annotations

The remove() methods should not be marked __exit unless we are using
platform_driver_probe() which disables unbinding device from driver
via sysfs.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>