mach-ux500: setting proper uart for snowball

The UART setting in uncompress.h changes on the Snowball board.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Robert Marklund <robert.marklund@stericsson.com>