ppc64: include/asm/md.h is not used any more

include/asm-ppc64/md.h

-/* 
- * md.h: High speed xor_block operation for RAID4/5 
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
- 
-#ifndef __ASM_MD_H
-#define __ASM_MD_H
-
-/* #define HAVE_ARCH_XORBLOCK */
-
-#define MD_XORBLOCK_ALIGNMENT	sizeof(long)
-
-#endif /* __ASM_MD_H */