drivers/rtc/rtc-ds1307.c: change sysfs function pointer assignment

The current usage of commas instead of semicolons is not wrong, but
affects the readability of the code.

Also, the code would break, if someone puts something between those two
assignments.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Cc: Austin Boyle <Austin.Boyle@aviatnet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>