PCI: rzg3s-host: Make configuration reset lines optional

PCI: rzg3s-host: Make configuration reset lines optional

Some SoC variants such as RZ/G3E handle configuration reset control through
PCIe AXI registers instead of dedicated reset lines. Make cfg_resets
optional by using devm_reset_control_bulk_get_optional_exclusive() to allow
SoCs to use alternative or complementary reset control mechanisms.

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> # RZ/V2N EVK
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://patch.msgid.link/20260306143423.19562-9-john.madieu.xa@bp.renesas.com