The SCP firmware on the ARM FPGA initialises the UART already. This allows
us to treat the PL011 as an SBSA Generic UART, which does not require
any further setup.

This in particular removes the need for any baudrate and base clock related
settings to be hard coded into the BL31 image.

Change-Id: I16fc943526267356b97166a7068459e06ff77f0f
Signed-off-by: Andre Przywara <andre.przywara@arm.com>