Patch 300-CVE-2015-8370.patch was added without proper rebasing on the
version used by OpenWrt, make it apply and refresh the patch to fix
compilation.
Fixes: 7e73e9128f ("grub2: Fix CVE-2015-8370")
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit 9ffbe84ea49fc643f41bfdf687de99aee17c9154)