switchtec: Use generic PCI Vendor ID and Class Code

switchtec: Use generic PCI Vendor ID and Class Code

Move the Microsemi Switchtec PCI Vendor ID (same as
PCI_VENDOR_ID_PMC_Sierra) to pci_ids.h.   Also, replace Microsemi class
constants with the standard PCI definitions.

Signed-off-by: Doug Meyer <[email protected]>
[bhelgaas: restore SPDX (I assume it was removed by mistake), remove
device ID definitions]
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Logan Gunthorpe <[email protected]>