Use FIELD_GET() to extract PCIe capability registers field instead of
custom masking and shifting.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230913122748.29530-9-ilpo.jarvinen@linux.intel.com


Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>