random: don't zap entropy count in rand_initialize()

The rand_initialize() function was being run fairly late in the kernel
boot sequence.  This was unfortunate, since it zero'ed the entropy
counters, thus throwing away credit that was accumulated earlier in
the boot sequence, and it also meant that initcall functions run
before rand_initialize were using a minimally initialized pool.

To fix this, fix init_std_data() to no longer zap the entropy counter;
it wasn't necessary, and move rand_initialize() to be an early
initcall.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>