drivers/rtc/rtc-mxc.c: remove defines already included in rtc.h

[akpm@linux-foundation.org: retain the code comments]
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Vladimir Zapolskiy <vzapolskiy@gmail.com>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>