drivers/rtc/rtc-s3c: use of_match_ptr() macro

This eliminates having an #ifdef returning NULL for the case when OF is
disabled.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>