net: mvpp2: cls: fix less than zero check on a u32 variable

The signed return from the call to mvpp2_cls_c2_port_flow_index is being
assigned to the u32 variable c2.index and then checked for a negative
error condition which is always going to be false. Fix this by assigning
the return to the int variable index and checking this instead.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: 90b509b3 ("net: mvpp2: cls: Add Classification offload support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2/mvpp2_cls.c

@@ -1029,12 +1029,14 @@ static int mvpp2_port_c2_tcam_rule_add(struct mvpp2_port *port,
 	struct flow_action_entry *act;
 	struct mvpp2_cls_c2_entry c2;
 	u8 qh, ql, pmap;
+	int index;
 
 	memset(&c2, 0, sizeof(c2));
 
-	c2.index = mvpp2_cls_c2_port_flow_index(port, rule->loc);
-	if (c2.index < 0)
+	index = mvpp2_cls_c2_port_flow_index(port, rule->loc);
+	if (index < 0)
 		return -EINVAL;
+	c2.index = index;
 
 	act = &rule->flow->action.entries[0];