drm/tests: Add test for drm_crtc_in_clone_mode()

Add kunit test to validate drm_crtc_in_clone_mode() helper

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241216-concurrent-wb-v4-2-fe220297a7f0@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>