xtensa: iss/network: make functions static

Make 2 functions static to prevent build warnings:

arch/xtensa/platforms/iss/network.c:204:16: warning: no previous prototype for 'tuntap_protocol' [-Wmissing-prototypes]
  204 | unsigned short tuntap_protocol(struct sk_buff *skb)
arch/xtensa/platforms/iss/network.c:444:6: warning: no previous prototype for 'iss_net_user_timer_expire' [-Wmissing-prototypes]
  444 | void iss_net_user_timer_expire(struct timer_list *unused)

Fixes: 7282bee7 ("xtensa: Architecture support for Tensilica Xtensa Part 8")
Fixes: d8479a21 ("xtensa: Convert timers to use timer_setup()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Message-Id: <20230920052139.10570-14-rdunlap@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/platforms/iss/network.c

@@ -201,7 +201,7 @@ static int tuntap_write(struct iss_net_private *lp, struct sk_buff **skb)
 	return simc_write(lp->tp.info.tuntap.fd, (*skb)->data, (*skb)->len);
 }
 
-unsigned short tuntap_protocol(struct sk_buff *skb)
+static unsigned short tuntap_protocol(struct sk_buff *skb)
 {
 	return eth_type_trans(skb, skb->dev);
 }
@@ -441,7 +441,7 @@ static int iss_net_change_mtu(struct net_device *dev, int new_mtu)
 	return -EINVAL;
 }
 
-void iss_net_user_timer_expire(struct timer_list *unused)
+static void iss_net_user_timer_expire(struct timer_list *unused)
 {
 }