crypto: ccp - invoke fallback for XTS ciphertext stealing

For correctness and compliance with the XTS-AES specification, we are
adding support for ciphertext stealing to XTS implementations, even
though no use cases are known that will be enabled by this.

Since the ccp driver already has a fallback skcipher standby for
dealing with input sizes other than [16, 512, 1024, 2048, 4096],
just drop the check against the block size.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gary Hook <gary.hook@amd.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>