Add SWITCHTEC_QUIRK() to reduce redundancy in declaring devices that use
quirk_switchtec_ntb_dma_alias().

By itself, this is no functional change, but a subsequent patch updates
SWITCHTEC_QUIRK() to fix ad281ecf ("PCI: Add DMA alias quirk for
Microsemi Switchtec NTB").

Fixes: ad281ecf ("PCI: Add DMA alias quirk for Microsemi Switchtec NTB")
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
[bhelgaas: split to separate patch]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>