s3c-rtc: remove unused variable

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>