crypto: rockchip - drop redundant crypto_skcipher_ivsize() calls

The function already initialized the ivsize variable
at the point of declaration, let's use it instead of
calling crypto_skcipher_ivsize() extra couple times.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 57d67c6 ("crypto: rockchip - rework by using crypto_engine")
Signed-off-by: Karina Yankevich <k.yankevich@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: Karina Yankevich

drivers/crypto/rockchip/rk3288_crypto_skcipher.c

@@ -321,8 +321,7 @@ static int rk_cipher_run(struct crypto_engine *engine, void *async_req)
 	algt->stat_req++;
 	rkc->nreq++;
 
-	ivsize = crypto_skcipher_ivsize(tfm);
-	if (areq->iv && crypto_skcipher_ivsize(tfm) > 0) {
+	if (areq->iv && ivsize > 0) {
 		if (rctx->mode & RK_CRYPTO_DEC) {
 			offset = areq->cryptlen - ivsize;
 			scatterwalk_map_and_copy(rctx->backup_iv, areq->src,