x86: Add /sys/firmware/memmap

[Bernhard Walle]

This patch series adds a new interface /sys/firmware/memmap
to export the BIOS (Firmware) provided memory map via sysfs
for usage with kexec.

While the first patch adds the generic interface, the second
patch implements that interface for E820 on x86. EFI is on the TODO
list, and other architectures can be added later.

This patch is RFC. It has been tested on x86-64 and i386 and
replaces my previous attemt that adds such an interface via
procfs.


Signed-off-by: Bernhard Walle <bwalle at suse.de>