time: Improve C99 compliance

Quote from Linux Programmer's Manual:
  "If t is non-NULL, the return value is also stored in the memory
   pointed to by t."

Change-Id: I8cb66b67e5f34c536ce2f0db76a6dc337c42ea3f
Signed-off-by: Jim Huang <jserv@0xlab.org>
1 file changed