hurd: Fix exposition of s/gettimeofday through timespec_s/get

conform/ISO11/time.h/linknamespace complains that using timespec_get exposes
gettimeofday.

conform/POSIX/time.h/linknamespace complains that using clock_settime
exposes settimeofday.

	* sysdeps/unix/clock_gettime.c (realtime_gettime, __clock_gettime): Use
	__gettimeofday instead of gettimeofday.
	* sysdeps/unix/clock_settime.c (__clock_settime): Use __settimeofday
	instead of settimeofday.