Remove io_index argument from cpu_register_io_memory()

The parameter is always zero except when registering the three internal
io regions (ROM, unassigned, notdirty).  Remove the parameter to reduce
the API's power, thus facilitating future change.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/omap_i2c.c b/hw/omap_i2c.c
index c0dd3a5..60da574 100644
--- a/hw/omap_i2c.c
+++ b/hw/omap_i2c.c
@@ -436,7 +436,7 @@
     s->bus = i2c_init_bus(NULL, "i2c");
     omap_i2c_reset(s);
 
-    iomemtype = cpu_register_io_memory(0, omap_i2c_readfn,
+    iomemtype = cpu_register_io_memory(omap_i2c_readfn,
                     omap_i2c_writefn, s);
     cpu_register_physical_memory(base, 0x800, iomemtype);
 
@@ -457,7 +457,7 @@
     s->bus = i2c_init_bus(NULL, "i2c");
     omap_i2c_reset(s);
 
-    iomemtype = l4_register_io_memory(0, omap_i2c_readfn,
+    iomemtype = l4_register_io_memory(omap_i2c_readfn,
                     omap_i2c_writefn, s);
     omap_l4_attach(ta, 0, iomemtype);