When calling to initialize the PL011 Uart, Rx buffer is
not cleared. In a 16550 uart device, during initialization,
the 16550's Fifo control registers would be used to clear
the Rx buffer, but no such register exists on PL011.
Modify the PL011 SerialPortInitialize function
to clear anything that was in the Rx buffer
after initialization is completed. This will prevent
any stale data from being interpreted as valid data.
Signed-off-by: Aaron Pop <aaronpop@microsoft.com>
aa980f0e12