tests/avocado: ppc test VOF bios Linux boot

VOF is the new lightweight fast pseries bios. Add a Linux boot test
using VOF.

More tests could be moved to use VOF becasue it's much faster, but
just dip one toe in the water first here. SLOF should continue to be
tested too.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

tests/avocado/ppc_pseries.py

@@ -29,6 +29,17 @@ def do_test_ppc64_linux_boot(self):
                          '-append', kernel_command_line)
         self.vm.launch()
 
+    def test_ppc64_vof_linux_boot(self):
+        """
+        :avocado: tags=arch:ppc64
+        :avocado: tags=machine:pseries
+        """
+
+        self.vm.add_args('-machine', 'x-vof=on')
+        self.do_test_ppc64_linux_boot()
+        console_pattern = 'VFS: Cannot open root device'
+        wait_for_console_pattern(self, console_pattern, self.panic_message)
+
     def test_ppc64_linux_boot(self):
         """
         :avocado: tags=arch:ppc64