pseries: Update SLOF firmware image

This fixes PCI bridges support regression.

This enables IOMMU support in virtio drivers.

The full list of changes is:

Alexey Kardashevskiy (12):
      allocator: Fix format strings for DEBUG
      virtio: Make virtio_set_qaddr static
      client: Load initramdisk location
      sloffs: Fix -Wunused-result gcc warnings in read/write
      pci-phb: Reimplement dma-map-in/out
      virtio: Store queue descriptors in virtio_device
      virtio-net: Init queues after features negotiation
      virtio: Enable IOMMU
      ibm,client-architecture-support: Fix stack handling
      fdt: Fix updating the tree at H_CAS
      version: update to 20191206
      version: update to 20191217

Michael Roth (1):
      dma: Define default dma methods for using by client/package instances

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-20191209.
+  built from git tag qemu-slof-20191217.
 
 - sgabios (the Serial Graphics Adapter option ROM) provides a means for
   legacy x86 software to communicate with an attached serial console as