timeout(9): change argument order for timeout_set_kclock()

timeout(9): change argument order for timeout_set_kclock()

Move the kclock argument before the flags argument.  XORing a bunch of
flags together may "sprawl", and I'd rather have any sprawl at the end
of the parameter list.

timeout_set_kclock() is undocumented and there is only one caller, so
no big refactor required.

Best to do this argument order shuffle before any bigger refactors of
e.g. timeout_set(9).