Update OpenBIOS images

Update OpenBIOS images to SVN r1280 built from submodule.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
diff --git a/pc-bios/README b/pc-bios/README
index 5914200..2bb6357 100644
--- a/pc-bios/README
+++ b/pc-bios/README
@@ -12,7 +12,7 @@
   1275-1994 (referred to as Open Firmware) compliant firmware.
   The included images for PowerPC (for 32 and 64 bit PPC CPUs),
   Sparc32 (including QEMU,tcx.bin and QEMU,cgthree.bin) and Sparc64 are built
-  from OpenBIOS SVN revision 1246.
+  from OpenBIOS SVN revision 1280.
 
 - SLOF (Slimline Open Firmware) is a free IEEE 1275 Open Firmware
   implementation for certain IBM POWER hardware.  The sources are at