pseries: Update SLOF

This patch updates the SLOF version, introducing a number of fixes:
 * add proper graphics support
 * fix bugs with graphical terminal under grub2
 * fix bugs in handling of 64-bit unit addresses
 * fix VSCSI representation to be closer to PowerVM
 * fix bugs which caused grub2 to crash

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
