tests/acceptance: Disable Spartan-3A DSP 1800A test

tests/acceptance: Disable Spartan-3A DSP 1800A test

This test is regularly failing on CI:

   (05/34) tests/acceptance/boot_linux_console.py:BootLinuxConsole.test_microblaze_s3adsp1800:
  Linux version 4.11.3 (thuth@thuth.remote.csb) (gcc version 6.4.0 (Buildroot 2018.05.2) ) #5 Tue Dec 11 11:56:23 CET 2018
  ...
  Freeing unused kernel memory: 1444K
  This architecture does not have kernel memory protection.
  [nothing happens here]
  Runner error occurred: Timeout reached (90.91 s)

This is a regression. Until someone figure out the problem,
disable the test to keep CI pipeline useful.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201109091719.2449141-1-f4bug@amsat.org>
Message-Id: <20201110192316.26397-9-alex.bennee@linaro.org>