kexec-tools: add patch to fix issue with appended DTB and zImage on ARM

kexec-tools: add patch to fix issue with appended DTB and zImage on ARM

This patch fixes a recently found problem when a zImage passed to
kexec-tools contains an appended DTB. In that case kexec boot fails because
the decompressor wrongly tries to use the non-existing appended DTB instaed
of the one passed in the register r2.

- http://lists.infradead.org/pipermail/kexec/2021-April/022353.html

Signed-off-by: Alexander Egorenkov <egorenar-dev@posteo.net>