PCI: imx6: Toggle the core reset for i.MX95 PCIe

Add toggling core reset for i.MX95 to align with PHY's power-up sequence.
Note that the register is named as IMX95_PCIE_COLD_RST in hardware, though
it is used to reset the PCIe core.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
[mani: subject and description rewording]
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20250416081314.3929794-4-hongxing.zhu@nxp.com