crypto: pcbc - remove ability to wrap internal ciphers

Following commit 944585a6 ("crypto: x86/aes-ni - remove special
handling of AES in PCBC mode"), it's no longer needed for the PCBC
template to support wrapping a cipher that has the CRYPTO_ALG_INTERNAL
flag set.  Thus, remove this now-unused functionality to make PCBC
consistent with the other single block cipher templates.

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