[ARM] S3C64XX: Show uncompress messages

Fix the initialisation of the fifo data in the uncompression serial
routines to ensure that if the FIFO is enabled, that the serial output
is not corrupted.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
[ben-linux@fluff.org: edit description to add more detail]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>