PCI: rzg3s-host: Add support for RZ/G3E PCIe controller

PCI: rzg3s-host: Add support for RZ/G3E PCIe controller

Add support for the PCIe controller found in RZ/G3E SoCs to the existing
RZ/G3S PCIe host controller driver. The RZ/G3E PCIe controller is similar
to the RZ/G3S, with the following key differences:

 - Supports PCIe Gen3 (8.0 GT/s) link speeds alongside Gen2 (5.0 GT/s)
 - Uses a different reset control mechanism via AXI registers instead
   of the Linux reset framework
 - Requires specific SYSC configuration for link state control and
   Root Complex mode selection

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
[mani: added a readl_relaxed() before fsleep() to flush previous write]
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/20260306143423.19562-13-john.madieu.xa@bp.renesas.com