hostapd: fix Proxy-ARP with Hotspot 2.0 disabled

The disable_dgaf config fiels is only available in case Hostapd is
compiled with Hotspot 2.0 support, however Proxy-ARP does not depend on
Hotspot 2.0.

Only add the code related to this config field when Hotspot 2.0 is
enabled to fix compilation with the aformentioned preconditions.

Signed-off-by: David Bauer <mail@david-bauer.net>

package/network/services/hostapd/patches/741-proxyarp-fix-compilation-with-Hotspot-2.0-disabled.patch

@@ -0,0 +1,51 @@
+From ad694836b2ded6b97b426bf331627537cdbff591 Mon Sep 17 00:00:00 2001
+From: David Bauer <mail@david-bauer.net>
+Date: Thu, 19 Aug 2021 00:52:04 +0200
+Subject: [PATCH] proxyarp: fix compilation with Hotspot 2.0 disabled
+
+The disable_dgaf config fiels is only available in case Hostapd is
+compiled with Hotspot 2.0 support, however Proxy-ARP does not depend on
+Hotspot 2.0.
+
+Only add the code related to this config field when Hotspot 2.0 is
+enabled to fix compilation with the aformentioned preconditions.
+
+Signed-off-by: David Bauer <mail@david-bauer.net>
+---
+ src/ap/dhcp_snoop.c  | 2 ++
+ src/ap/ndisc_snoop.c | 2 ++
+ 2 files changed, 4 insertions(+)
+
+--- a/src/ap/dhcp_snoop.c
++++ b/src/ap/dhcp_snoop.c
+@@ -88,6 +88,7 @@ static void handle_dhcp(void *ctx, const
+ 		}
+ 	}
+
++#ifdef CONFIG_HS20
+ 	if (hapd->conf->disable_dgaf && is_broadcast_ether_addr(buf)) {
+ 		for (sta = hapd->sta_list; sta; sta = sta->next) {
+ 			if (!(sta->flags & WLAN_STA_AUTHORIZED))
+@@ -96,6 +97,7 @@ static void handle_dhcp(void *ctx, const
+ 							    (u8 *) buf, len);
+ 		}
+ 	}
++#endif
+
+ 	if (msgtype == DHCPACK) {
+ 		if (b->your_ip == 0)
+--- a/src/ap/ndisc_snoop.c
++++ b/src/ap/ndisc_snoop.c
+@@ -151,10 +151,12 @@ static void handle_ndisc(void *ctx, cons
+ 				return;
+ 		}
+ 		break;
++#ifdef CONFIG_HS20
+ 	case ROUTER_ADVERTISEMENT:
+ 		if (hapd->conf->disable_dgaf)
+ 			ucast_to_stas(hapd, buf, len);
+ 		break;
++#endif
+ 	case NEIGHBOR_ADVERTISEMENT:
+ 		if (hapd->conf->na_mcast_to_ucast)
+ 			ucast_to_stas(hapd, buf, len);