Introduce Selinux policies for the mainline supplicant.

Aside from binder access, supplicant requires some
networking capabilities in order to work as expected.

Bug: 365585450
Test: Manual test - retrieve the mainline supplicant
      binder in frameworks/base, and call a test
      method using its AIDL interface
Change-Id: Id76fe09b2ecae758ed93b92d92020d45f19d2501
diff --git a/private/system_server.te b/private/system_server.te
index 6eb5b74..044edc1 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -304,6 +304,7 @@
 binder_call(system_server, logd)
 binder_call(system_server, wificond)
 binder_call(system_server, uprobestats)
+binder_call(system_server, wifi_mainline_supplicant)
 binder_service(system_server)
 
 # Use HALs
@@ -1023,6 +1024,7 @@
 userdebug_or_eng(`
   allow system_server profcollectd_service:service_manager find;
 ')
+allow system_server wifi_mainline_supplicant_service:service_manager find;
 
 add_service(system_server, batteryproperties_service)