drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()

Start using the new helper that does the refcounted
allocations.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>
Link: https://lore.kernel.org/r/20250331-b4-panel-refcounting-v4-4-dad50c60c6c9@redhat.com


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