contrib: update ffmpeg to release 4.4

Change-Id: Ia231c1b7749cce1bfb220f869d8a48283979f0ca
diff --git a/GreenScreen/ffmpeg/rules.mak b/GreenScreen/ffmpeg/rules.mak
index 7b06d39..3990332 100644
--- a/GreenScreen/ffmpeg/rules.mak
+++ b/GreenScreen/ffmpeg/rules.mak
@@ -1,4 +1,4 @@
-FFMPEG_HASH := 9f38fac053010205806ece11e6aea9b7d3bde041
+FFMPEG_HASH := n4.4
 FFMPEG_URL := https://git.ffmpeg.org/gitweb/ffmpeg.git/snapshot/$(FFMPEG_HASH).tar.gz
 
 PKGS+=ffmpeg