staging: lustre: replace cfs_srand() calls with add_device_randomness().

The only places that cfs_srand is called, the random bits are
mixed with bits from get_random_bytes().  So it is equally effective
to add entropy to either pool.
So we can replace calls to cfs_srand() with calls that add the
entropy with add_device_randomness().  That function adds time-based
entropy, so we can discard the ktime_get_ts64 calls.

One location in lustre_handles.c only adds timebased
entropy.  This cannot improve the entropy provided by get_random_bytes(),
so just discard that call.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>