crypto: algapi - enforce that all instances have a ->free() method
All instances need to have a ->free() method, but people could forget to
set it and then not notice if the instance is never unregistered. To
help detect this bug earlier, don't allow an instance without a ->free()
method to be registered, and complain loudly if someone tries to do it.
Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>