Make -mtdblock optional again.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4639 c046a42c-6fe2-441c-8c8c-71466251a162

hw/nand.c

@@ -450,14 +450,11 @@ struct nand_flash_s *nand_init(int manf_id, int chip_id)
         cpu_abort(cpu_single_env, "%s: Unsupported NAND chip ID.\n",
                         __FUNCTION__);
     }
-    index = drive_get_index(IF_MTD, 0, 0);
-    if (index == -1) {
-        cpu_abort(cpu_single_env, "%s: missing MTD device\n",
-                        __FUNCTION__);
-    }
 
     s = (struct nand_flash_s *) qemu_mallocz(sizeof(struct nand_flash_s));
-    s->bdrv = drives_table[index].bdrv;
+    index = drive_get_index(IF_MTD, 0, 0);
+    if (index != -1)
+        s->bdrv = drives_table[index].bdrv;
     s->manf_id = manf_id;
     s->chip_id = chip_id;
     s->size = nand_flash_ids[s->chip_id].size << 20;