drm/tests: Handle EDEADLK in set_up_atomic_state()

drm/tests: Handle EDEADLK in set_up_atomic_state()

Fedora/CentOS/RHEL CI is reporting intermittent failures while running
the drm_validate_modeset test [1]:

    # drm_test_check_connector_changed_modeset: EXPECTATION FAILED at
    # drivers/gpu/drm/tests/drm_atomic_state_test.c:162
    Expected ret == 0, but
        ret == -35 (0xffffffffffffffdd)

Change the set_up_atomic_state() helper function to return on error and
restart the atomic sequence when the returned error is EDEADLK.

[1] https://s3.amazonaws.com/arr-cki-prod-trusted-artifacts/trusted-artifacts/2106744096/test_x86_64/11762450343/artifacts/jobwatch/logs/recipes/19797909/tasks/204139142/results/945095586/logs/dmesg.log

Fixes: 73d934d7b6e3 ("drm/tests: Add test for drm_atomic_helper_commit_modeset_disables()")
Closes: https://datawarehouse.cki-project.org/issue/4004
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patch.msgid.link/20251104102535.12212-2-jose.exposito89@gmail.com