[ARM] pxa: allow display of uncompress message through STUART

Some boards use UART other than FFUART for the console, E.g. Marvell
PXA3xx Form Factor Platform (aka Littleton) uses STUART. This patch
modifies the uncompress.h so that display of the uncompress message
is routed to the STUART.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>