net: marvell: prestera: fix memory leak in prestera_rxtx_switch_init()

When prestera_sdma_switch_init() failed, the memory pointed to by
sw->rxtx isn't released. Fix it. Only be compiled, not be tested.

Fixes: 501ef30 ("net: marvell: prestera: Add driver for Prestera family ASIC devices")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Vadym Kochan <vadym.kochan@plvision.eu>
Link: https://lore.kernel.org/r/20221108025607.338450-1-shaozhengchao@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/prestera/prestera_rxtx.c

@@ -776,14 +776,19 @@ static netdev_tx_t prestera_sdma_xmit(struct prestera_sdma *sdma,
 int prestera_rxtx_switch_init(struct prestera_switch *sw)
 {
 	struct prestera_rxtx *rxtx;
+	int err;
 
 	rxtx = kzalloc(sizeof(*rxtx), GFP_KERNEL);
 	if (!rxtx)
 		return -ENOMEM;
 
 	sw->rxtx = rxtx;
 
-	return prestera_sdma_switch_init(sw);
+	err = prestera_sdma_switch_init(sw);
+	if (err)
+		kfree(rxtx);
+
+	return err;
 }
 
 void prestera_rxtx_switch_fini(struct prestera_switch *sw)