Allow drmserver to read the wv keys.

Bug: 8539042
Change-Id: I31e7a3ae6ba783b78c3b38756966950a20f2f2aa

drmserver.te

@@ -23,3 +23,4 @@ allow drmserver tee_device:chr_file rw_file_perms;
 allow drmserver platform_app_data_file:file { read write getattr };
 allow drmserver app_data_file:file { read write getattr };
 allow drmserver sdcard_type:file { read write getattr };
+allow drmserver efs_file:file { open read getattr };