crypto: cryptd - Use crypto_aead_set_reqsize helper

This patch uses the crypto_aead_set_reqsize helper to avoid directly
touching the internals of aead.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/cryptd.c b/crypto/cryptd.c
index b0602ba..e1584fb 100644
--- a/crypto/cryptd.c
+++ b/crypto/cryptd.c
@@ -729,7 +729,8 @@
 
 	crypto_aead_set_flags(cipher, CRYPTO_TFM_REQ_MAY_SLEEP);
 	ctx->child = cipher;
-	tfm->crt_aead.reqsize = sizeof(struct cryptd_aead_request_ctx);
+	crypto_aead_set_reqsize(__crypto_aead_cast(tfm),
+				sizeof(struct cryptd_aead_request_ctx));
 	return 0;
 }