kexec: export PG_hwpoison flag into vmcoreinfo

This patch exports a PG_hwpoison into vmcoreinfo when
CONFIG_MEMORY_FAILURE is defined.  "makedumpfile" needs to read
information of memory, such as 'mem_section', 'zone', 'pageflags' from
vmcore.

We introduce a function into "makedumpfile" to exclude hwpoison page from
vmcore dump.  In order to introduce this function, PG_hwpoison flag have
to export into vmcoreinfo.

Signed-off-by: Mitsuhiro Tanino <mitsuhiro.tanino.gm@hitachi.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Mitsuhiro Tanino <mitsuhiro.tanino.gm@hitachi.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>