drm/tests: hdmi: Reorder DRM entities variables assignment

[ Upstream commit 6b6bfd63 ]

The tests all deviate slightly in how they assign their local pointers
to DRM entities. This makes refactoring pretty difficult, so let's just
move the assignment as soon as the entities are allocated.

Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20250129-test-kunit-v2-3-fe59c43805d5@kernel.org


Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>