Permissions for input_native_boot flags

For input experiments that are enabled at boot time, allow system_server
to read and write the device config flags.

Bug: 120794829
Test: presubmit
Change-Id: I0f075a7579c593d4e07c3e31be529e34554068a6
diff --git a/private/system_server.te b/private/system_server.te
index 8648738..30235e5 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -582,6 +582,7 @@
 set_prop(system_server, cppreopt_prop)
 
 # server configurable flags properties
+set_prop(system_server, device_config_input_native_boot_prop)
 set_prop(system_server, device_config_netd_native_prop)
 
 # BootReceiver to read ro.boot.bootreason
@@ -935,6 +936,7 @@
   -system_server
   -flags_health_check
 } {
+  device_config_input_native_boot_prop
   device_config_netd_native_prop
 }:property_service set;