Most siginfo_to_lsiginfo callers already zeroed the l_siginfo_t before
callit it, but linux_waitid did not. Instead of zeroing in the called
function to address linux_waitid (as in commit 2e6ebe70), just do it in
linux_waitid.
admbugs: 765
Reported by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
Reviewed by: Andrew
MFC after: 1 day
Security: Kernel stack memory disclosure
Sponsored by: The FreeBSD Foundation
