Now that different UARTs share the same console_t struct, we can
simplify the console selection for the Marvell platforms:
We share the same console_t pointers, just change the name of the
console register functions, depending on the selected platform.

Change-Id: I6fe3e49fd7f208a9b3372c5deef43236a12867bc
Signed-off-by: Andre Przywara <andre.przywara@arm.com>