Store MemoryRegion in RAMBlock

As a step in moving live migration from RAMBlocks to MemoryRegions,
store the MemoryRegion in a RAMBlock.

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/exec.c b/exec.c
index dffceb9..a4116d9 100644
--- a/exec.c
+++ b/exec.c
@@ -2793,6 +2793,7 @@
     size = TARGET_PAGE_ALIGN(size);
     new_block = g_malloc0(sizeof(*new_block));
 
+    new_block->mr = mr;
     new_block->offset = find_ram_offset(size);
     if (host) {
         new_block->host = host;