ARM: mach-shmobile: mackerel: SCIF port for earlyprintk when using zboot

Initialise the SCIF serial port to allow earlyprintk
output when using zboot. It is based on a very similar
patched for AP4EB.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>