xen/ia64: fix build breakage because of conflicting u64 guest handles

include/xen/interface/xen.h:526: error: conflicting types for ‘__guest_handle_u64’
arch/ia64/include/asm/xen/interface.h:74: error: previous declaration of ‘__guest_handle_u64’ was here

Problem introduced by "xen/granttable: Introducing grant table V2 stucture"

which added a new definition to include/xen/interface/xen.h for "u64".

Fix: delete the ia64 arch specific definition.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>