[IA64] __copy_user breaks on unaligned src

memcpy_mck.S::__copy_user breaks in the prefetch code under these conditions :-

* src is unaligned and
* dst is near the end of a page and
* the page after dst is unmapped.
Signed-off-by: NKeith Owens <kaos@sgi.com>
Signed-off-by: NTony Luck <tony.luck@intel.com>

arch/ia64/lib/memcpy_mck.S

@@ -300,7 +300,7 @@ EK(.ex_handler,	(p[D])	st8 [dst1] = t15, 4*8)
 	add	src_pre_mem=0,src0	// prefetch src pointer
 	add	dst_pre_mem=0,dst0	// prefetch dest pointer
 	and	src0=-8,src0		// 1st src pointer
-(p7)	mov	ar.lc = r21
+(p7)	mov	ar.lc = cnt
 (p8)	mov	ar.lc = r0
 	;;
 	TEXT_ALIGN(32)