pv-grub: correct sizeof usage

We were lucky that sizeof(frame) >= sizeof(*frame) anyway.

Signed-off-by: Matthew Daley <mattd@bugfuzz.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

stubdom/grub/mini-os.c

@@ -333,7 +333,7 @@ struct frame {
 static void minios_transmit (struct nic *nic, const char *d, unsigned int t,
                              unsigned int s, const char *p)
 {
-    struct frame *frame = alloca(sizeof(frame) + s);
+    struct frame *frame = alloca(sizeof(*frame) + s);
 
     memcpy(frame->dest, d, ETH_ALEN);
     memcpy(frame->src, nic->node_addr, ETH_ALEN);