crypto: drbg - Delete unused ctx from struct sdesc

The ctx array in struct sdesc is never used.  Delete it as it's
bogus since the previous member ends with a flexible array.

Reported-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: herbertx

crypto/drbg.c

@@ -1443,7 +1443,6 @@ static void drbg_kcapi_set_entropy(struct crypto_rng *tfm,
 #if defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_HMAC)
 struct sdesc {
 	struct shash_desc shash;
-	char ctx[];
 };
 
 static int drbg_init_hash_kernel(struct drbg_state *drbg)