tests/avocado/tuxrun_baselines.py: improve code coverage for ppc64

tests/avocado/tuxrun_baselines.py: improve code coverage for ppc64

Commit c0c8687ef0fd990db8db1655a8a6c5a5e35dd4bb disabled the
boot_linux.py test-case due to which the code coverage for ppc
decreased by around 2%. As per the discussion on
https://lore.kernel.org/qemu-devel/87sfdpqcy4.fsf@linaro.org/ it
was mentioned that the baseline test for ppc64 could be modified
to make up this 2% code coverage. This patch attempts to achieve
this 2% code coverage by adding various device command line
arguments (to ./qemu-system-ppc64) in the tuxrun_baselines.py
test-case.

The code coverage report with boot_linux.py, without it and finally
with these tuxrun_baselines.py changes is as follows:

With boot_linux.py
------------------
  lines......: 13.8% (58006 of 420997 lines)
  functions..: 20.7% (7675 of 36993 functions)
  branches...: 9.2% (22146 of 240611 branches)
Without boot_linux.py (without this patch changes)
--------------------------------------------------
  lines......: 11.9% (50174 of 420997 lines)
  functions..: 18.8% (6947 of 36993 functions)
  branches...: 7.4% (17580 of 239017 branches)
Without boot_linux.py (with this patch changes)
-----------------------------------------------
  lines......: 13.8% (58287 of 420997 lines)
  functions..: 20.7% (7640 of 36993 functions)
  branches...: 8.4% (20223 of 240611 branches)

Rebased on Alex Benee's testing/next branch:
https://gitlab.com/stsquad/qemu/-/tree/testing/next

Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Reported-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230424041830.1275636-1-kconsul@linux.vnet.ibm.com>
Message-Id: <20230424092249.58552-13-alex.bennee@linaro.org>