kernel - Rejigger random number generator to be per-cpu 2/2

kernel - Rejigger random number generator to be per-cpu 2/2

* The initializer tries to diverge each cpu's csprng a bit more
  now.  These initial conditions are not intended to produce secure
  random numbers, but they should be reasonably secure by the time the
  kernel is finished booting.

* Once the csprng is operational, do not always inject the same
  entropy into both csprngs since that would make having two and
  XOR'ing the results together kinda worthless.

* If RDRAND is available the csprng will get new injections 25 times
  a second on each cpu.  Without it, however, entropy injection is
  relatively slow.