crypto: arm64/aes-ccm - Keep NEON enabled during skcipher walk

Now that kernel mode NEON no longer disables preemption, we no longer
have to take care to disable and re-enable use of the NEON when calling
into the skcipher walk API. So just keep it enabled until done.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>