tools/mkimage: update to 2020.04

also change the download source to https and add a mirror
drop merged patches

Signed-off-by: Lucian Cristian <lucian.cristian@gmail.com>
[Add extra changes to compile on FreeBSD, merge two patches]
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

tools/mkimage/patches/070-remove_generated_autoconf.patch

@@ -0,0 +1,10 @@
+--- a/tools/imximage.c
++++ b/tools/imximage.c
+@@ -11,7 +11,6 @@
+ #include "imagetool.h"
+ #include <image.h>
+ #include "imximage.h"
+-#include <generated/autoconf.h>
+ 
+ #define UNDEFINED 0xFFFFFFFF
+