crypto: allwinner - Add allwinner subdirectory

Since a second Allwinner crypto driver will be added, it is better to
create a dedicated subdirectory.

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>