pseries: Update SLOF firmware image

This adds vTPM support, full-FDT-rebuild-on-CAS fixes and
basic ext4 support.

The full changelog is:

Alexey Kardashevskiy (10):
      disk-label: Prepare for extenting
      disk-label: Support Linux GPT partition type
      ext2: Prepare for extending
      ext2: Rename group-desc-size
      ext2: Read size of group descriptors
      ext2: Read all 64bit of inode number
      ext2/4: Add basic extent tree support
      elf64: Add LE64 ABIv1/2 support for loading images to given address
      fdt: Fix creating new nodes at H_CAS
      version: update to 20200221

Greg Kurz (2):
      fdt: Fix update of "interrupt-controller" node at CAS
      fdt: Delete nodes of devices removed between boot and CAS

Stefan Berger (8):
      slof: Implement SLOF_get_keystroke() and SLOF_reset()
      slof: Make linker script variables accessible
      qemu: Make print_version variable accessible
      tpm: Add TPM CRQ driver implementation
      tpm: Add sha256 implementation
      tcgbios: Add TPM 2.0 support and firmware API
      tcgbios: Implement menu to clear TPM 2 and activate its PCR banks
      tcgbios: Measure the GPT table

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

pc-bios/README

@@ -14,7 +14,7 @@
 - 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-20191217.
+  built from git tag qemu-slof-20200221.
 
 - sgabios (the Serial Graphics Adapter option ROM) provides a means for
   legacy x86 software to communicate with an attached serial console as