drivers/rtc/rtc-pcf8563.c: simplify return from function

This commit does not change any logic here.  It just makes the code easier
to read.

This is how it looked like:
If err != 0 return err;
else return 0;

Signed-off-by: Robert Kmiec <robert.r.kmiec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>