Give serial number access to drm hal server not client

Bug: 284812208
Change-Id: I489feba47f9eb0d9a4ea483cd55aa3a8bbfd389e
diff --git a/public/hal_drm.te b/public/hal_drm.te
index 43d0a7c..34ca0b2 100644
--- a/public/hal_drm.te
+++ b/public/hal_drm.te
@@ -12,7 +12,7 @@
 allow hal_drm self:process execmem;
 
 # Permit reading device's serial number from system properties
-get_prop(hal_drm, serialno_prop)
+get_prop(hal_drm_server, serialno_prop)
 
 # Read files already opened under /data
 allow hal_drm system_data_file:file { getattr read };