Add mmd selinux policies

This adds minimum selinux policies to unblock these functions which are
already submitted:

* The init service launchs mmd as a native daemon by mmd.rc.
* mmd exposes binder API.

EXCEPTION_NO_FUZZER in build/soong/service_fuzzer_bindings.go is allowed
for Rust products.

Bug: 375432644
Bug: 370509309
Test: confirmed mmd is launched after: adb shell aflags enable \
   android.mmd.flags.mmd_enabled; adb reboot

Change-Id: Ibd3e68e5aea83b3bc4a01e9dcf00be2daf2466c1
diff --git a/private/service_contexts b/private/service_contexts
index 4fc9435..fbdc081 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -354,6 +354,7 @@
 meminfo                                   u:object_r:meminfo_service:s0
 memtrack.proxy                            u:object_r:memtrackproxy_service:s0
 midi                                      u:object_r:midi_service:s0
+mmd                                       u:object_r:mmd_service:s0
 mount                                     u:object_r:mount_service:s0
 music_recognition                         u:object_r:music_recognition_service:s0
 nearby                                    u:object_r:nearby_service:s0