To support .mxmf which is specified in Android CDD.

Bug: 7082658
Change-Id: I21269d72d1d21627c6adb2e6fbcb078d0eda6020
Tested: checked MediaScanner scans .mxmf and Music app plays .mxmf file.
diff --git a/media/libmediaplayerservice/MediaPlayerFactory.cpp b/media/libmediaplayerservice/MediaPlayerFactory.cpp
index f821cc3..3f69c11 100644
--- a/media/libmediaplayerservice/MediaPlayerFactory.cpp
+++ b/media/libmediaplayerservice/MediaPlayerFactory.cpp
@@ -246,6 +246,7 @@
                                                  ".midi",
                                                  ".smf",
                                                  ".xmf",
+                                                 ".mxmf",
                                                  ".imy",
                                                  ".rtttl",
                                                  ".rtx",