isa: Fix documentation of isa_register_portio_list()

Commit b40acf9 (ioport: Switch dispatching to memory core layer,
2013-06-24) removed all instances of old_portio.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>

include/hw/isa/isa.h

@@ -78,7 +78,7 @@ void isa_register_ioport(ISADevice *dev, MemoryRegion *io, uint16_t start);
  * @dev: the ISADevice against which these are registered; may be NULL.
  * @start: the base I/O port against which the portio->offset is applied.
  * @portio: the ports, sorted by offset.
- * @opaque: passed into the old_portio callbacks.
+ * @opaque: passed into the portio callbacks.
  * @name: passed into memory_region_init_io.
  */
 void isa_register_portio_list(ISADevice *dev, uint16_t start,