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>
random: initialize the last_time field in struct timer_rand_state

Since we initialize jiffies to wrap five minutes before boot (see
INITIAL_JIFFIES defined in include/linux/jiffies.h) it's important to
make sure the last_time field is initialized to INITIAL_JIFFIES.
Otherwise, the entropy estimator will overestimate the amount of
entropy resulting from the first call to add_timer_randomness(),
generally by about 8 bits.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
random: add debugging code to detect early use of get_random_bytes()

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

Conflicts:
	drivers/char/random.c