sensecap_m2: Update wifi mac calculation.

According to the Seeed SenseCAP M2 label on the back of the gateway,
the wifi mac should be ethernet mac - 1.

Author: brocaar

conf/seeed_sensecap_m2/files/etc/hotplug.d/net/10-set-wifi-mac

@@ -4,6 +4,6 @@
 . /lib/functions.sh
 . /lib/functions/system.sh
 
-uci set wireless.@wifi-iface[0].macaddr=$(macaddr_add "$(mtd_get_mac_binary factory 0x2e)" 1)
+uci set wireless.@wifi-iface[0].macaddr=$(macaddr_add "$(mtd_get_mac_binary factory 0x2e)" -1)
 uci commit wireless
 wifi reload