Updated test library to fix test dependence on BP status

Created by: kipmacsaigoren

Added in handling of UART tx empty interrupts during the UART data wait section of the test library. Before, the issue was that with BP off, the UART test would read out a tx empty error from the LSR during the final UART data wait. This issue did not show up when the BP on. Now it gets handled by the program and the correct values are read out of UART no matter the status of the branch predictor.