rtc: omap: remove incorrect __exit markups

Even if bus is not hot-pluggable, devices can be unbound from the
driver via sysfs, so we should not be using __exit annotations on
remove() methods. The only exception is drivers registered with
platform_driver_probe(), which specifically disables sysfs bind/unbind
attributes.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>