Allow system server to map zygote_tmpfs files.

Needed for an ART optimization.

Test: build
Change-Id: I120cdbe410248ac08f4e56cdeb6588681630a964
diff --git a/private/system_server.te b/private/system_server.te
index ee4cfe2..66f9ba4 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -20,7 +20,7 @@
 # Create a socket for connections from zygotes.
 type_transition system_server system_data_file:sock_file system_unsolzygote_socket "unsolzygotesocket";
 
-allow system_server zygote_tmpfs:file read;
+allow system_server zygote_tmpfs:file { map read };
 allow system_server appdomain_tmpfs:file { getattr map read write };
 
 # For Incremental Service to check if incfs is available