test/py: Avoid pulling in Labgrid with tests

When Labgrid is installed as an editable package (pip install -e),
pytest automatically loads it as a plugin. This can interfere with
U-Boot's test suite.

Disable automatic loading of the Labgrid pytest plugin to prevent
conflicts.

Signed-off-by: Simon Glass <simon.glass@canonical.com>

test/py/pytest.ini

@@ -5,6 +5,7 @@
 # Static configuration data for pytest. pytest reads this at startup time.
 
 [pytest]
+addopts = -p no:labgrid
 markers =
     boardspec: U-Boot: Describes the set of boards a test can/can't run on.
     buildconfigspec: U-Boot: Describes Kconfig/config-header constraints.