libpayload: add time()

Change-Id: I97e393537ccc71ea454bb0d6cdbbb7ed32485f1e
Signed-off-by: Nicola Corna <nicola@corna.info>
Reviewed-on: https://review.coreboot.org/21011
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

payloads/libpayload/include/time.h

@@ -44,6 +44,7 @@ struct timeval {
 	suseconds_t tv_usec; /**< Microseconds */
 };
 
+time_t time(time_t *tp);
 int gettimeofday(struct timeval *tv, void *tz);
 /** @} */