Set min_sdk_version

codecs_g711dec is missing min_sdk_version while it is available to
com.android.media.swcodec (which targets Q)

Likewise, libmedia_datasource_headers is set min_sdk_version as well
because it is used by com.android.media.

Bug: 152655956
Test: m
Change-Id: I93b90792f1650de898ff6a5687984b599329411f
diff --git a/media/libmedia/Android.bp b/media/libmedia/Android.bp
index eefea91..a9f734d 100644
--- a/media/libmedia/Android.bp
+++ b/media/libmedia/Android.bp
@@ -28,6 +28,7 @@
         "//apex_available:platform",
         "com.android.media",
     ],
+    min_sdk_version: "29",
 }
 
 filegroup {