In the merge tree, commit 
0458060c1c59c5378d8fb5daabe18cf4681c35cd
broke boot on some machines because the initialization of conswitchp
was moved to arch/powerpc/kernel/setup_64.c, but a corresponding copy
was not added to arch/ppc64/kernel/setup.c.  This patch fixes it.
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
        /* initialize the syscall map in systemcfg */
        setup_syscall_map();
 
+#ifdef CONFIG_DUMMY_CONSOLE
+       conswitchp = &dummy_con;
+#endif
+
        ppc_md.setup_arch();
 
        /* Use the default idle loop if the platform hasn't provided one. */