pseries: Update SLOF firmware image

This has really just one fix from Stefan, the rest is housekeeping.

The full changelog is:

Alexey Kardashevskiy (3):
      Revert "make: Define default rule for .c when V=1 or V=2"
      js2x: Fix compile and cleanup
      version: update to 20211112

Stefan Berger (1):
      tcgbios: Disable platform hierarchy in case of failure

Thomas Huth (8):
      Mention the CR vs. LF problem in the documentation
      slof/fs/accept: Replace TABs with spaces
      Fix the URL to the Linux kernel coding style
      lib/libc/README.txt: Fix "cannel" typo
      travis.yml: Fix keywords
      travis.yml: Update to Focal Fossa
      travis.yml: Compile-test the qemu build
      Silence some trivial compiler warning in the js2x code

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

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-20210711.
+  built from git tag qemu-slof-20211112.
 
 - VOF (Virtual Open Firmware) is a minimalistic firmware to work with
   -machine pseries,x-vof=on. When enabled, the firmware acts as a slim shim and

SLOF @ a6906b02

-Subproject commit dd0dcaa1c1085c159ddab709c7f274b3917be8bd
+Subproject commit a6906b024c6cca5a86496f51eb4bfee3a0c36148