net: wwan: t7xx: Fix return type of t7xx_ccmni_start_xmit

The ndo_start_xmit field in net_device_ops is expected to be of type
netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of t7xx_ccmni_start_xmit should be changed from int to
netdev_tx_t.
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Acked-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Link: https://lore.kernel.org/r/20220912214510.929070-1-nhuck@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/wwan/t7xx/t7xx_netdev.c

@@ -74,7 +74,7 @@ static int t7xx_ccmni_send_packet(struct t7xx_ccmni *ccmni, struct sk_buff *skb,
 	return 0;
 }
 
-static int t7xx_ccmni_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t t7xx_ccmni_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct t7xx_ccmni *ccmni = wwan_netdev_drvpriv(dev);
 	int skb_len = skb->len;