migration: Export ram.c functions in its own file

All functions are internal except for ram_mig_init().  Create
migration/misc.h for this kind of functions.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
diff --git a/migration/migration.c b/migration/migration.c
index ec79aff..6e5afa4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -22,6 +22,7 @@
 #include "fd.h"
 #include "socket.h"
 #include "rdma.h"
+#include "ram.h"
 #include "migration/migration.h"
 #include "savevm.h"
 #include "qemu-file-channel.h"