Remove unused includes and forward declarations in libmediaextractor/include

Test: make checkbuild
Bug: 67908556
Change-Id: If840305af5c043bb8014590eb208cf11c99e61ee
diff --git a/media/libmedia/nuplayer2/GenericSource.cpp b/media/libmedia/nuplayer2/GenericSource.cpp
index 6d5b14d..094af7e 100644
--- a/media/libmedia/nuplayer2/GenericSource.cpp
+++ b/media/libmedia/nuplayer2/GenericSource.cpp
@@ -26,6 +26,7 @@
 #include <media/DataSource.h>
 #include <media/MediaBufferHolder.h>
 #include <media/IMediaExtractorService.h>
+#include <media/IMediaSource.h>
 #include <media/MediaHTTPService.h>
 #include <media/MediaExtractor.h>
 #include <media/MediaSource.h>