rtc: don't use __exit_p to wrap ds1302_rtc_remove

The function ds1302_rtc_remove is defined using __devexit, so don't use
__exit_p but __devexit_p to wrap it.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: linux-kernel@vger.kernel.org
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: rtc-linux@googlegroups.com
Signed-off-by: Paul Mundt <lethal@linux-sh.org>