crypto/ipsec_mb: fix premature dereference

[ upstream commit 8c60a04 ]

This patch removes coverity defect CID 374380:
Null pointer dereferences  (REVERSE_INULL)

Coverity issue: CID 374380
Fixes: 918fd2f ("crypto/ipsec_mb: move aesni_mb PMD")

Signed-off-by: Piotr Bronowski <piotrx.bronowski@intel.com>

drivers/crypto/ipsec_mb/ipsec_mb_private.h

@@ -191,13 +191,13 @@ ipsec_mb_parse_xform(const struct rte_crypto_sym_xform *xform,
 			const struct rte_crypto_sym_xform **cipher_xform,
 			const struct rte_crypto_sym_xform **aead_xform)
 {
-	const struct rte_crypto_sym_xform *next = xform->next;
-
 	if (xform == NULL) {
 		*mode = IPSEC_MB_OP_NOT_SUPPORTED;
 		return -ENOTSUP;
 	}
 
+	const struct rte_crypto_sym_xform *next = xform->next;
+
 	if (xform->type == RTE_CRYPTO_SYM_XFORM_CIPHER) {
 		if (next == NULL) {
 			if (xform->cipher.op == RTE_CRYPTO_CIPHER_OP_ENCRYPT) {