FreeBSD: Use new SYSCTL_SIZEOF()

SYSCTL_SIZEOF() has been introduced in FreeBSD by commit "sysctl(9):
Ease exporting struct sizes; Discourage doing that" (713abc9880aa) in
branch 'main'.  It will soon be backported to 'stable/14'.  We will thus
be able to remove the old, alternate version left in the '#else' branch
as soon as 'stable/13' goes out of support (April 30, 2026).

Sponsored-by:   The FreeBSD Foundation
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Olivier Certner <[email protected]>
Closes #17309

Author: OlCe2

module/os/freebsd/zfs/zfs_znode_os.c

@@ -67,8 +67,12 @@
 #include "zfs_comutil.h"
 
 /* Used by fstat(1). */
+#ifdef SYSCTL_SIZEOF
+SYSCTL_SIZEOF(znode, znode_t);
+#else
 SYSCTL_INT(_debug_sizeof, OID_AUTO, znode, CTLFLAG_RD,
 	SYSCTL_NULL_INT_PTR, sizeof (znode_t), "sizeof(znode_t)");
+#endif
 
 /*
  * Define ZNODE_STATS to turn on statistic gathering. By default, it is only