soc: fsl: dpio: fix dereference of pointer p before null check

Pointer p is currently being dereferenced before it is null
checked on a memory allocation failure check. Fix this by
checking if p is null before dereferencing it.

Addresses-Coverity: ("Dereference before null check")
Fixes: 3b2abda7 ("soc: fsl: dpio: Replace QMAN array mode with ring mode enqueue")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>

drivers/soc/fsl/dpio/qbman-portal.c

@@ -249,10 +249,11 @@ struct qbman_swp *qbman_swp_init(const struct qbman_swp_desc *d)
 	u32 mask_size;
 	u32 eqcr_pi;
 
-	spin_lock_init(&p->access_spinlock);
-
 	if (!p)
 		return NULL;
+
+	spin_lock_init(&p->access_spinlock);
+
 	p->desc = d;
 	p->mc.valid_bit = QB_VALID_BIT;
 	p->sdq = 0;