[PATCH] Fix broken initialization of conswitchp for ARCH=ppc64

In the merge tree, commit 0458060c
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>

arch/ppc64/kernel/setup.c

@@ -1039,6 +1039,10 @@ void __init setup_arch(char **cmdline_p)
 	/* 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. */