edited xps_library/\@xps_dram/gen_mhs_ip.m to change the ddr3_controller variable DDR3_APP to ddr3_ctrl instead of ddr3_app.  this change allows us to insert the OPB interface when previously it was not accounted for.  As of now, no plans to relabel DDR3_APP variable in the ddr3_controller files, but the naming discrepancy is noted.