tests/avocado: add explicit timeout for ppc64le TCG tests

We don't want to rely on the soon to be reduced default time. These
tests are still slow for something we want to run in CI though.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220914155950.804707-6-alex.bennee@linaro.org>

tests/avocado/boot_linux.py

@@ -115,6 +115,8 @@ class BootLinuxPPC64(LinuxTest):
     :avocado: tags=arch:ppc64
     """
 
+    timeout = 180
+
     def test_pseries_tcg(self):
         """
         :avocado: tags=machine:pseries