powerpc/cell/edac: Log a syndrome code in case of correctable error

If correctable error occurs the syndrome code was logged as 0. This patch
lets EDAC to log a correct syndrome code to make problem investigation
easier.

Signed-off-by: Maxim Shchetynin <maxim@de.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>