ramips-mt7621: use phy1 MAC address as primary on DIR-860L B1

package/gluon-core/files/lib/gluon/upgrade/010-primary-mac

@@ -27,6 +27,8 @@ end
 
 if platform.match('ar71xx', 'generic', {'tl-wdr3600', 'tl-wdr4300'}) then
   table.insert(try_files, 1, '/sys/class/ieee80211/phy1/macaddress')
+elseif platform.match('ramips', 'mt7621', {'dir-860l-b1'}) then
+  table.insert(try_files, 1, '/sys/class/ieee80211/phy1/macaddress')
 elseif platform.match('ar71xx', 'generic', {'unifi-outdoor-plus', 'carambola2',
                                             'mr600', 'mr600v2',
                                             'mr900', 'mr900v2',