PCI: tegra194: Use FIELD_GET()/FIELD_PREP() with Link Width fields

PCI: tegra194: Use FIELD_GET()/FIELD_PREP() with Link Width fields

Use FIELD_GET() to extract PCIe Negotiated Link Width field instead of
custom masking and shifting.

Similarly, change custom code that misleadingly used
PCI_EXP_LNKSTA_NLW_SHIFT to prepare value for PCI_EXP_LNKCAP write
to use FIELD_PREP() with correct field define (PCI_EXP_LNKCAP_MLW).

Link: https://lore.kernel.org/r/20230919125648.1920-5-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>