NASR-M board bring-up, DDR3 test

Today is an important milestone in a board bring-up, as the DDR3 subsystem appears functional. I was able to run a Vivado bundled Zynq bare-metal DDR test with no errors. The test image was uploaded via JTAG and executed on a CPU core. That was the most important indication of a system's health to me. Even if other subsystems don’t work properly, I’ll be able to respin the board with minimal…