powerpc/pseries: Remove syslog prefix in uncompressed oops text

Removal of syslog prefix in the uncompressed oops text will
help in capturing more oops data.

Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>