signals: make siginfo_t si_utime + si_sstime report times in USER_HZ, not HZ

In the switch to configurable HZ in 2.6, the treatment of the si_utime and
si_stime fields that are exposed to userland via the siginfo structure
looks to have been botched.  As things stand, these fields report times in
units of HZ, so that userland gets information that varies depending on
the HZ that the kernel was configured with.  This patch changes the
reported values to use USER_HZ units.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>