Cleanups and passing memory ranges via e820 table instead of memmap=

[Thomas Renninger]

These patches are against latest kexec-tool master branch from:
git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools

The cleanups are intended to do no functional change.

The patches got successfully tested on one platform.
Also the e820 passing should introduce no change.
Whether the memmap=exactmap ... is passed and the crash kernel makes up
the e820 table from memmap=X#Y and similar params or whether exactly the
same ranges are passed via e820 in bootloader structure directly should not
matter at all.