Make the option structures const.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
diff --git a/extensions/libxt_physdev.c b/extensions/libxt_physdev.c
index 0f862c0..5517472 100644
--- a/extensions/libxt_physdev.c
+++ b/extensions/libxt_physdev.c
@@ -25,7 +25,7 @@
 "\n", IPTABLES_VERSION);
 }
 
-static struct option opts[] = {
+static const struct option opts[] = {
 	{ "physdev-in", 1, 0, '1' },
 	{ "physdev-out", 1, 0, '2' },
 	{ "physdev-is-in", 0, 0, '3' },