pseries: Update SLOF firmware image to qemu-slof-20151103

The changes are:
1. supports recent binutils;
2. 64bit BARs behind PCI bridges supported;
3. Many fixes for USB keyboard support - keys, XHCI;
4. virtio-vga support.

This image was built with:
gcc version 4.8.3 20140911 (Red Hat 4.8.3-7) (GCC)
GNU ld version 2.23.2

The full changelog is:
  > version: update to 20151103
  > documentation: Add a clause about signing off
  > qemu/js2x/client: Support binutils >= 2.25.1
  > Fix special keys on USB
  > Fix function keys on USB
  > pci-scan: program 64-bit mem bar range in pci-bridge bar
  > Allow to build SLOF on Little Endian host
  > usb-xhci: add keyboard support
  > usb-xhci: ready the link trb early
  > usb-xhci: scan usb high speed ports
  > usb-xhci: bulk improve event handling loop
  > usb-xhci: return on allocation failure
  > usb-xhci: add delay in shutdown path
  > usb-xhci: event trbs does not need link trb
  > usb-hid: refactor usb key reading
  > takeover: Fix header includes
  > board-js2x: Add missing file dma-function.fs
  > vga: Add support for virtio-vga
  > qemu-vga: Use MMIO BAR instead of legacy IO ports
  > slof: Change call_c() function to a proper assembler function

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

pc-bios/README

@@ -17,7 +17,7 @@
 - SLOF (Slimline Open Firmware) is a free IEEE 1275 Open Firmware
   implementation for certain IBM POWER hardware.  The sources are at
   https://github.com/aik/SLOF, and the image currently in qemu is
-  built from git tag qemu-slof-20150813.
+  built from git tag qemu-slof-20151103.
 
 - sgabios (the Serial Graphics Adapter option ROM) provides a means for
   legacy x86 software to communicate with an attached serial console as

roms/SLOF

@@ -1 +1 @@
-Subproject commit 811277ac91f674a9273e2b529791e9b75350f3e8
+Subproject commit b4c93802a5b2c72f096649c497ec9ff5708e4456