sim:config: Change UART5 from PTY to socket connection

Use the socket connection instead of PTY so there's no FIFO deadlock
created by the unconnected PTY device during the robot test.

zmodem doesn't work with the socket connect, and we need to work with
Antmicro team on that.

Change-Id: Ia9b44d461b1870c6827c4448a2a19f8d20693375