PCI: dwc: Add support for configuring lane equalization presets

PCI: dwc: Add support for configuring lane equalization presets

PCIe equalization presets are predefined settings used to optimize signal
integrity by compensating for signal loss and distortion in high-speed data
transmission.

Based upon the number of lanes and the data rate supported, write the
preset data read from the device tree in to the lane equalization control
registers. These preset values will be used by the controller during the
LTSSM lane equalization procedure.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: reworded the commit message and comments in the driver]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://patch.msgid.link/20250328-preset_v6-v9-5-22cfa0490518@oss.qualcomm.com