media: rzg2l-cru: csi2: Skip system clock for RZ/V2H(P) SoC

The RZ/V2H(P) SoC does not require a `system` clock for the CSI-2
interface. To accommodate this, introduce a `has_system_clk` bool flag
in the `rzg2l_csi2_info` structure and update the rzg2l_csi2_probe() to
conditionally request the clock only when needed.

This patch is in preparation for adding support for RZ/V2H(P) SoC.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://lore.kernel.org/r/20250411170624.472257-10-tommaso.merciai.xr@bp.renesas.com


Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>