Add SePolicy for system_server accessing sysfs uhid.

Add SePolicy to allow Android input manager accessing sysfs uhid folder.

Bug: 161633432
Test: dumpsys input and watch for input device battery status.
Change-Id: I6ed1ab45f1cff409982c36627e12e62667819f37
diff --git a/private/system_server.te b/private/system_server.te
index 95d7cc7..7193ffb 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -355,6 +355,8 @@
 allow system_server sysfs_power:file rw_file_perms;
 allow system_server sysfs_thermal:dir search;
 allow system_server sysfs_thermal:file r_file_perms;
+allow system_server sysfs_uhid:dir r_dir_perms;
+allow system_server sysfs_uhid:file rw_file_perms;
 
 # TODO: Remove when HALs are forced into separate processes
 allow system_server sysfs_vibrator:file { write append };
@@ -1243,6 +1245,15 @@
   -system_server
 } wifi_config_prop:file no_rw_file_perms;
 
+# Only allow system server to write uhid sysfs files
+neverallow {
+    domain
+    -init
+    -system_server
+    -ueventd
+    -vendor_init
+} sysfs_uhid:file no_w_file_perms;
+
 # BINDER_FREEZE is used to block ipc transactions to frozen processes, so it
 # can be accessed by system_server only (b/143717177)
 # BINDER_GET_FROZEN_INFO is used by system_server to determine the state of a frozen binder