hwrng: ks-sa - Enable COMPILE_TEST

This patch enables COMPILE_TEST on the ks-sa-rng driver.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>