kexec_file: add kexec_file flag to support debug printing
    
    Resolves: https://issues.redhat.com/browse/RHEL-35640
    Upstream Status: git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
    Conflict: None
    
    commit 9d9cf8de8b2ad8273861a30476a46f34cd34871a
    Author: Baoquan He <bhe@redhat.com>
    Date:   Tue Nov 14 23:20:30 2023 +0800
    
        kexec_file: add kexec_file flag to support debug printing
    
        This add KEXEC_FILE_DEBUG to kexec_file_flags so that it can be passed
        to kernel when '-d' is added with kexec_file_load interface. With that
        flag enabled, kernel can enable the debugging message printing.
    
        Signed-off-by: Baoquan He <bhe@redhat.com>
        Signed-off-by: Simon Horman <horms@kernel.org>
    
    Signed-off-by: Baoquan He <bhe@redhat.com>