vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer

vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer

Modern kernel marks the end of ELF note buffer with NT_VMCORE_PAD type
note in order to make the buffer satisfy mmap()'s page-size boundary
requirement.  This patch makes finishing reading each buffer if the note
type now being read is NT_VMCORE_PAD type.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>