[undi] Ensure that native drivers are tried before the UNDI PCI driver

Suggested-by: Alessandro Salvatori <sandr8@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/drivers/net/undi.c

 PCI_ROM ( 0xffff, 0xffff, "undipci", "UNDI (PCI)", 0 ),
 };
 
-struct pci_driver undipci_driver __pci_driver = {
+struct pci_driver undipci_driver __pci_driver_fallback = {
 	.ids = undipci_nics,
 	.id_count = ( sizeof ( undipci_nics ) / sizeof ( undipci_nics[0] ) ),
 	.probe = undipci_probe,

src/include/ipxe/pci.h

 /** Declare a PCI driver */
 #define __pci_driver __table_entry ( PCI_DRIVERS, 01 )
 
+/** Declare a fallback PCI driver */
+#define __pci_driver_fallback __table_entry ( PCI_DRIVERS, 02 )
+
 #define PCI_BUS( busdevfn )		( ( (busdevfn) >> 8 ) & 0xff )
 #define PCI_SLOT( busdevfn )		( ( (busdevfn) >> 3 ) & 0x1f )
 #define PCI_FUNC( busdevfn )		( ( (busdevfn) >> 0 ) & 0x07 )