Try to iImplement mul_u64_u64_div_u64() -- really? -- with a 2nd attemptfor an updated iwlwifi driver (though
to deal with overflows up-towe do not yet use it the point of reducing precisionre; it is used for in-kernel ptp on wifi).
Sponsored by: The FreeBSD Foundation
Submitted by: cperciva
MFC after: 10 days