kexec: Support copying of kernel tagged list (atags) in the decompressor.
This is needed to hardboot kexec a kernel with a new tags list (including a
new kernel command line), since the new atags would otherwise be lost with
the limited kernel memory mapping.  Without this patch, a hardboot-kexec'd
kernel uses the atags provided by the bootloader.

Orgin Code from https://github.com/mkasick/android_kernel_samsung_d2spr/commit/9c53b1ea99f52533b2fdc34f4332e6dcc638737e

Signed-off-by: cholokei <leesl0416@naver.com>