Allow boot without a drive on Sparc machines (partly extracted from Xen)

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4997 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/hw/boards.h b/hw/boards.h
index 22ac332..e6dd198 100644
--- a/hw/boards.h
+++ b/hw/boards.h
@@ -16,6 +16,7 @@
     QEMUMachineInitFunc *init;
 #define RAMSIZE_FIXED	(1 << 0)
     ram_addr_t ram_require;
+    int nodisk_ok;
     struct QEMUMachine *next;
 } QEMUMachine;