CorebootPayloadPkg: Use correct BaseSerialPortLib16550

CorebootPayloadPkg: Use correct BaseSerialPortLib16550

Use the BaseSerialPortLib16550 which sets RTS and DTR during
initialization.  This fixes the mis-matched flow control issue when
the flow control signals are connected between the host and target
and the host has flow control enabled.

Change-Id: I3505e129b2de3c5c17fff23c62553f15cd892dca
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-by: Maurice Ma <maurice.ma@intel.com>
Reviewed-by: Prince Agyeman <prince.agyeman@intel.com>