atsam3u - Flush uart buffers on baud rate change
atsam3u - Flush uart buffers on baud rate change

Add code to flush the UART buffers when the baud rate is changed.
This fixes a bug in mbed testing where serial data on a failed test
can show up in a subsequent test.

google/DAPLink-port,google/DAPLink-port,sg-/DAPLink,google/DAPLink-port,sg-/DAPLink,google/DAPLink-port,sg-/DAPLink