Handle integer overflows correctly when converting msecs and secs to
ticks and vice versa.
These issues were caught by recently added panic() calls on INVARIANTS
systems.

Reported by: syzbot+b44787b4be7096cd1590@syzkaller.appspotmail.com
Reported by: syzbot+35f82d22805c1e899685@syzkaller.appspotmail.com
MFC after: 1 week