pack-revindex.c: rearrange xcalloc arguments

xcalloc() takes two arguments: the number of elements and their size.
init_pack_revindex() passes the arguments in reverse order, passing the
size of a pack_revindex, followed by the number to allocate.

Rearrange them so they are in the correct order.

Signed-off-by: Brian Gesiak <modocache@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pack-revindex.c

@@ -45,7 +45,7 @@ static void init_pack_revindex(void)
 	if (!num)
 		return;
 	pack_revindex_hashsz = num * 11;
-	pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
+	pack_revindex = xcalloc(pack_revindex_hashsz, sizeof(*pack_revindex));
 	for (p = packed_git; p; p = p->next) {
 		num = pack_revindex_ix(p);
 		num = - 1 - num;