crypto: simd - allow registering multiple algorithms at once

Add a function to crypto_simd that registers an array of skcipher
algorithms, then allocates and registers the simd wrapper algorithms for
them.  It assumes the naming scheme where the names of the underlying
algorithms are prefixed with two underscores.

Also add the corresponding 'unregister' function.

Most of the x86 crypto modules will be able to use these.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>