The arm_fpga port requires a DTB, to launch a BL33 payload.
To make this port more flexible, we can also use the information in the
DT to configure the console driver.
For a start, find the DT node pointed to by the stdout-path property, and
read the base address from there.
This assumes for now that the stdout-path points to a PL011 UART.

This allows to remove platform specific addresses from the image. We
keep the original base address for the crash console.

Change-Id: I46a990de2315f81cae4d7913ae99a07b0bec5cb1
Signed-off-by: Andre Przywara <andre.przywara@arm.com>