crypto: api - Disallow cryptomgr as a module if algorithms are built-in

If we have at least one algorithm built-in then it no longer makes
sense to have the testing framework, and hence cryptomgr to be a
module.  It should be either on or off, i.e., built-in or disabled.

This just happens to stop a potential runaway modprobe loop that
seems to trigger on at least one distro.

With fixes from Evgeniy Polyakov.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>