pseries: Update SLOF firmware image

This patch updates the SLOF submodule and precompiled image.  The new
SLOF versions contains two changes of note:

 * The previous SLOF has a bug in SCSI condition handling that was
   exposed by recent updates to qemu's SCSI emulation.  This update
   fixes the bug.

 * The previous SLOF has a bug in its addressing of SCSI devices,
   which can be exposed under certain conditions.  The new SLOF also
   fixes this.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
