crypto: algapi - remove crypto_alloc_instance()

Now that all "blkcipher" templates have been converted to "skcipher",
crypto_alloc_instance() is no longer used.  And it's not useful any
longer as it creates an old-style weakly typed instance rather than a
new-style strongly typed instance.  So remove it, and now that the name
is freed up rename crypto_alloc_instance2() to crypto_alloc_instance().

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