kexec/uefi: copy secure boot flag in boot params across kexec reboot
    
    Kexec reboot in case secure boot enabled does not keep the secure boot mode
    in new kernel, so later one can load unsigned kernel via legacy kexec_load.
    
    Adding a patch to fix this by retain the secure_boot flag in original kernel.
    
    Signed-off-by: Dave Young <dyoung@redhat.com>