For the keyboard inputs to be functional in the WinPE Special
Administration Console (SAC), enable the hardware flow control
and DC4 commands only for the UART port that used as the WinPE
SAC display.

Change-Id: Ieb7ad25472d75e1852a0e4a0b252ab5099e64cc4
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>