migration: fix -Werror=maybe-uninitialized false-positives

../migration/dirtyrate.c:186:5: error: ‘records’ may be used uninitialized [-Werror=maybe-uninitialized]
../migration/dirtyrate.c:168:12: error: ‘gen_id’ may be used uninitialized [-Werror=maybe-uninitialized]
../migration/migration.c:2273:5: error: ‘file’ may be used uninitialized [-Werror=maybe-uninitialized]

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Hyman Huang <yong.huang@smartx.com>
diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 5478d58..233acb0 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -149,12 +149,12 @@
                                  unsigned int flag,
                                  bool one_shot)
 {
-    DirtyPageRecord *records;
+    DirtyPageRecord *records = NULL;
     int64_t init_time_ms;
     int64_t duration;
     int64_t dirtyrate;
     int i = 0;
-    unsigned int gen_id;
+    unsigned int gen_id = 0;
 
 retry:
     init_time_ms = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
diff --git a/migration/migration.c b/migration/migration.c
index ae2be31..021faee 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2278,7 +2278,7 @@
  */
 static void migration_release_dst_files(MigrationState *ms)
 {
-    QEMUFile *file;
+    QEMUFile *file = NULL;
 
     WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
         /*