- try_inc_mod_count() already does what crypto_alg_get() was trying to do.
(feedback from Andrew Morton).
- Moved the BUG_ON() in crypto_unregister_alg() further up, no need to
bother iterating over the list.
- Always use kmap_atomic (feedback from Andrew Morton).  Implemented two
atomic kmaps, KM_USER for user context and KM_SOFTIRQ for softirq
context.
- Fixup KM_CRYPTO_ placement so Dave does not go crazy.