a3700: Use generic console_t data structure

Since now the generic console_t structure holds the UART base address as
well, let's use that generic location and drop the UART driver specific
data structure at all.

Change-Id: I89c3ab2ed85ab941d8b38ced48474feb4aaa8b7e
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
3 files changed