Commit 69b6f2e8 ("crypto: arm64/aes-neon - limit exposed routines if
faster driver is enabled") intended to hide modes from the plain NEON
driver that are also implemented by the faster bit sliced NEON one if
both are enabled. However, the defined() CPP function does not detect
if the bit sliced NEON driver is enabled as a module. So instead, let's
use IS_ENABLED() here.

Fixes: 69b6f2e8 ("crypto: arm64/aes-neon - limit exposed routines if ...")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>