drivers/rtc/rtc-pcf2123.c: initialize dynamic sysfs attributes

Dynamically allocated sysfs attributes must be initialized using
sysfs_attr_init(), otherwise lockdep complains: BUG: key <address> not in
.data!

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Ilya Shchepetkov <shchepetkov@ispras.ru>
Cc: Chris Verges <chrisv@cyberswitching.com>
Cc: Christian Pellegrin <chripell@fsfe.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>