[IA64] Delete erroneous copy_page.o in global lib-y list

copy_page.o appeared twice in arch/ia64/lib/Makefile. The
one in global lib-y is wrong where it should be just in
lib-$(CONFIG_ITANIUM).

Both copy_page.o and copy_page_mck.o are build for Itanium2
processor and the link order will pick up the low performing
copy_page function (originally written for itanium processor).
In this case, we really want the copy_page_mck.o for optimized
version.

Signed-off-by: Kenneth Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>