ARM: S3C: move s3c_adc_remove to .devexit.text

The function s3c_adc_remove is used only wrapped by __devexit_p so define
it using __devexit.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-By: Ben Dooks <ben@simtec.co.uk>
Cc: Ramax Lo <ramaxlo@gmail.com>
Cc: Nelson Castillo <arhuaco@freaks-unidos.net>
Cc: linux-kernel@vger.kernel.org
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Ryan Mallon <ryan@bluewatersys.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Ben Dooks <ben-linux@fluff.org>