vmstate, memory: decouple vmstate from memory API

Currently creating a memory region automatically registers it for
live migration.  This differs from other state (which is enumerated
in a VMStateDescription structure) and ties the live migration code
into the memory core.

Decouple the two by introducing a separate API, vmstate_register_ram(),
for registering a RAM block for migration.  Currently the same
implementation is reused, but later it can be moved into a separate list,
and registrations can be moved to VMStateDescription blocks.

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/memory.c b/memory.c
index 93f9569..f7b3d50 100644
--- a/memory.c
+++ b/memory.c
@@ -1033,7 +1033,6 @@
 }
 
 void memory_region_init_ram(MemoryRegion *mr,
-                            DeviceState *dev,
                             const char *name,
                             uint64_t size)
 {
@@ -1041,12 +1040,11 @@
     mr->ram = true;
     mr->terminates = true;
     mr->destructor = memory_region_destructor_ram;
-    mr->ram_addr = qemu_ram_alloc(dev, name, size, mr);
+    mr->ram_addr = qemu_ram_alloc(size, mr);
     mr->backend_registered = true;
 }
 
 void memory_region_init_ram_ptr(MemoryRegion *mr,
-                                DeviceState *dev,
                                 const char *name,
                                 uint64_t size,
                                 void *ptr)
@@ -1055,7 +1053,7 @@
     mr->ram = true;
     mr->terminates = true;
     mr->destructor = memory_region_destructor_ram_from_ptr;
-    mr->ram_addr = qemu_ram_alloc_from_ptr(dev, name, size, ptr, mr);
+    mr->ram_addr = qemu_ram_alloc_from_ptr(size, ptr, mr);
     mr->backend_registered = true;
 }
 
@@ -1073,7 +1071,6 @@
 void memory_region_init_rom_device(MemoryRegion *mr,
                                    const MemoryRegionOps *ops,
                                    void *opaque,
-                                   DeviceState *dev,
                                    const char *name,
                                    uint64_t size)
 {
@@ -1082,7 +1079,7 @@
     mr->opaque = opaque;
     mr->terminates = true;
     mr->destructor = memory_region_destructor_rom_device;
-    mr->ram_addr = qemu_ram_alloc(dev, name, size, mr);
+    mr->ram_addr = qemu_ram_alloc(size, mr);
     mr->ram_addr |= cpu_register_io_memory(memory_region_read_thunk,
                                            memory_region_write_thunk,
                                            mr,