vl: Tighten parsing of -machine option phandle_start

Make it QEMU_OPT_NUMBER, so it gets parsed by generic code, which
actually bothers to check for errors, rather than its user, which
doesn't.

Cc: Alexander Graf <agraf@suse.de>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
Message-id: 1372943363-24081-8-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index fb69f22..bea1a10 100644
--- a/vl.c
+++ b/vl.c
@@ -409,7 +409,7 @@
             .help = "Dump current dtb to a file and quit",
         }, {
             .name = "phandle_start",
-            .type = QEMU_OPT_STRING,
+            .type = QEMU_OPT_NUMBER,
             .help = "The first phandle ID we may generate dynamically",
         }, {
             .name = "dt_compatible",