uncompress.h now saves the selected UART's physical address in Tegra's
IRAM, along with a cookie to indicate validity.

The first time it's run, macro addruart in debug-macro.S looks for this
cookie, and if it's present, uses the UART address stored there. If not,
the static value TEGRA_DEBUG_UART_BASE is used, as was previous behaviour.
The static behaviour will thus be used when not booting using a zImage.

This work was inspired by work by Doug Anderson <dianders@chromium.org>;
see http://lkml.org/lkml/2011/9/26/284. However, this patch relies on
the data passing describe above, rather than duplicating the UART
selection logic in debug-macro.S; the latest selection logic is more
complex due to the need to check reset/clock bits too.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>