tegra124: Implement and enable serial console support for tegra124.

The driver is very similar to the 8250 driver, except it isn't in two parts,
and it also spaces its registers 4 bytes apart instead of having them directly
adjacent to each other.

Also, eliminate the UART test function in the bootblock. It's no longer needed
since the actual console output serves the same purpose.

Right now the clock divisor is fixed for now, and we'll want to actually
figure out what value to use at some point.

TEST=Built for link, pit, nyan and lumpy. Booted into the bootblock on nyan
and saw serial output on the console.

Change-Id: Idd659222901eb76b0ed8cbb986deb5124096f2f6
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/171337
Reviewed-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
4 files changed