The arm64 kernel will shortly disallow nested kernel mode NEON.

So honour this in the ARMv8 Crypto Extensions implementation of
CCM-AES, and fall back to a scalar implementation using the generic
crypto helpers for AES, XOR and incrementing the CTR counter.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>