crypto: sunxi-ss - Add MODULE_ALIAS to sun4i-ss

The MODULE_ALIAS is required to enable the sun4i-ss driver to load
automatically when built at a module. Tested on a Cubietruck.

Fixes: 6298e948 ("crypto: sunxi-ss - Add Allwinner Security System crypto accelerator")
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>