vmdk: Remove unnecessary initialization

It will be assigned to the return value of vmdk_read_desc.
Suggested-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NDon Koch <dkoch@verizon.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1417649314-13704-6-git-send-email-famz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/vmdk.c

@@ -914,7 +914,7 @@ exit:
 static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
 {
-    char *buf = NULL;
+    char *buf;
     int ret;
     BDRVVmdkState *s = bs->opaque;
     uint32_t magic;