tile: switch to GENERIC_PCI_IOMAP

tile now has working stubs for ioport_map and ioremap
such that the generic pci_iomap will DTRT: cast to
pointer on memory and return NULL and log message on IO map.

Switch it over to GENERIC_PCI_IOMAP.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>