Revert "kmssink: change hold buffer number to 3"

This reverts commit ba15e45751e03ce16617af2249b6850e39326225.

this commit was a work around that fix video jitter when enable
DTRC. Test the latest kernel, without the commit, video playback
is ok when enable DTRC

Conflicts:
	sys/kms/gstkmssink.h
diff --git a/sys/kms/gstkmssink.h b/sys/kms/gstkmssink.h
index 7178266..ed3801c 100644
--- a/sys/kms/gstkmssink.h
+++ b/sys/kms/gstkmssink.h
@@ -45,7 +45,7 @@
 #define GST_IS_KMS_SINK_CLASS(klass) \
   (G_TYPE_CHECK_CLASS_TYPE((klass), GST_TYPE_KMS_SINK))
 
-#define DEFAULT_HOLD_BUFFER_NUM 3
+#define DEFAULT_HOLD_BUFFER_NUM 2
 
 typedef struct _GstKMSSink GstKMSSink;
 typedef struct _GstKMSSinkClass GstKMSSinkClass;