[PATCH 1/3] Use vmcoreinfo note in /proc/kcore for --mem-usage option

kernel commit 23c85094fe18 added vmcoreinfo note to /proc/kcore.
Use the vmcoreinfo note to get necessary information, especially
page_offset and phys_base on arm64, for the --mem-usage option.

Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>