mdadm: update criteria to build with corosync

mdadm: update criteria to build with corosync

mdadm only works with corosync 2.x which provides header file corosync/cmap.h.
If build mdadm with corosync 1.x, it fails with:

| member.c:12:27: fatal error: corosync/cmap.h: No such file or directory
|  #include <corosync/cmap.h>
|                            ^

Build with corosync only header file corosync/cmap.h exists.

Ref:
https://github.com/neilbrown/mdadm/blob/master/mdadm.h#L63

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>