drm: renesas: rz-du: Add atomic_pre_enable

drm: renesas: rz-du: Add atomic_pre_enable

When drm_panel.prepare_prev_first is set to true in a panel driver, the
panel expects the MIPI DSI hardware to be already configured before the
panel's prepare function is called because it might need to send DCS
commands.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Tested-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20250521210335.3149065-1-chris.brandt@renesas.com