Bump Buildroot to 2021.02-rc3 (#1260)

* Rebase patches to Buildroot 2021.02-rc3

* Update Buildroot to 2021.02-rc3

* Declare Kernel headers to be Linux version 5.10 (since they are, and new Buildroot knows about 5.10)

buildroot/package/ffmpeg/0004-avformat-mpegts-make-sure-mpegts-read-header-always.patch

@@ -0,0 +1,38 @@
+From 3136f41e6db8189994a8e4f72eacc92b669776d1 Mon Sep 17 00:00:00 2001
+From: Marton Balint <cus@passwd.hu>
+Date: Sun, 15 Nov 2020 00:39:41 +0100
+Subject: [PATCH] avformat/mpegts: make sure mpegts_read_header always stops at
+ the first pmt
+
+mpegts_read_header stops parsing the file at the first PMT. However the check
+that ensured this was wrong because streams can also be added before the first
+PMT is received (e.g. EIT).
+
+So let's make sure we are in the header reading phase by checking if ts->pkt is
+unset instead of checking if the number of streams found so far is 0.
+
+Downloaded from Kodi ffmpeg repo:
+https://github.com/xbmc/FFmpeg/commit/3136f41e6db8189994a8e4f72eacc92b669776d1
+
+Patch was committed upstream:
+http://git.videolan.org/?p=ffmpeg.git;a=patch;h=ca55240b8c1fd4cfdb61f88fd2cb378d475d910a
+
+Signed-off-by: Marton Balint <cus@passwd.hu>
+Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
+---
+ libavformat/mpegts.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
+index c6fd3e1cef63..1da81a0fe62a 100644
+--- a/libavformat/mpegts.c
++++ b/libavformat/mpegts.c
+@@ -2352,7 +2352,7 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
+         goto out;
+ 
+     // stop parsing after pmt, we found header
+-    if (!ts->stream->nb_streams)
++    if (!ts->pkt)
+         ts->stop_parse = 2;
+ 
+     set_pmt_found(ts, h->id);