systemd-conf: Add bbappend for WiFi hotspot network config file

Together with hostapd this will give us all we need to run a very basic
WiFi hotspot setup. DHCP, DNS and NAT for the clients to serve.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>

meta-ohos-blueprints/recipes-core/systemd/files/80-wireless.network

+[Match]
+Name=wlan0
+
+[Network]
+Address=172.16.47.1/24
+DHCPServer=true
+IPMasquerade=true
+
+[DHCPServer]
+PoolOffset=100
+PoolSize=50
+EmitDNS=yes
+DNS=9.9.9.9 8.8.8.8

meta-ohos-blueprints/recipes-core/systemd/systemd-conf_%.bbappend

+FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
+
+SRC_URI_append = "file://80-wireless.network"
+
+do_install_append() {
+    install -D -m0644 ${WORKDIR}/80-wireless.network ${D}${systemd_unitdir}/network/
+}