microblaze: Use asm-generic/io.h

Using generic io.h will narrow down code duplication
in architecture io.h.

- define PCI_IOBASE
- remove non existing pci_io_base extern

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/mm/consistent.c

@@ -117,7 +117,7 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *dma_handle)
 	ret = (void *)va;
 
 	/* This gives us the real physical address of the first page. */
-	*dma_handle = pa = virt_to_bus((void *)vaddr);
+	*dma_handle = pa = __virt_to_phys(vaddr);
 #endif
 
 	/*