crypto: sunxi-ss - prevent compilation on 64-bit

The driver for the sunxi-ss crypto engine is not entirely 64-bit safe,
compilation on arm64 spits some warnings.
The proper fix was deemed to involved [1], so since 64-bit SoCs won't
have this IP block we just disable this driver for 64-bit.

[1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/399988.html


     (and the reply)

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>