[PATCH net-next] ipv6: fix "'ioam6_if_id_max' defined but not used" warn

When compiling without CONFIG_SYSCTL, this warning appears:

  net/ipv6/addrconf.c:99:12: error: 'ioam6_if_id_max' defined but not used [-Werror=unused-variable]
     99 | static u32 ioam6_if_id_max = U16_MAX;
        |            ^~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

Simply moving the declaration of this variable under ...

  #ifdef CONFIG_SYSCTL

... with other similar variables fixes the issue.

Fixes: 9ee11f0fff20 ("ipv6: ioam: Data plane support for Pre-allocated Trace")
Signed-off-by: Matthieu Baerts <redacted>
---

Notes:
    Please note that this 'ioam6_if_id_max' variable could certainly be
    declared as 'const' like some others used as limits for sysctl knobs.
    But here, this patch focuses on fixing the warning reported by GCC.

 net/ipv6/addrconf.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1802287977f1..db0a89810f28 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c

@@ -96,8 +96,6 @@
 #define IPV6_MAX_STRLEN \
 	sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")
 
-static u32 ioam6_if_id_max = U16_MAX;
-
 static inline u32 cstamp_delta(unsigned long cstamp)
 {
 	return (cstamp - INITIAL_JIFFIES) * 100UL / HZ;

@@ -6550,6 +6548,7 @@ static int addrconf_sysctl_disable_policy(struct ctl_table *ctl, int write,
 
 static int minus_one = -1;
 static const int two_five_five = 255;
+static u32 ioam6_if_id_max = U16_MAX;
 
 static const struct ctl_table addrconf_sysctl[] = {
 	{

-- 
2.31.1