Blackfin arch: Fix bug using usb keyboard crashes kernel

Without conswitchp preset, we have the following situation:

 - During initcalls: con_init is called, and returns because of
   !display_desc.

 - At this point there is no memory allocated for vc_cons[].d
   A bit later vty_init calls kbd_init.

 - From now on events are passed to kbd_event which will then call
   kbd_keycode.

 - kbd_keycode will oops on a NULL pointer dereference on vc->vc_tty
Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NBryan Wu <bryan.wu@analog.com>
[ Added commit description based on email thread. - Linus ]
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/blackfin/kernel/setup.c

@@ -33,7 +33,6 @@
 #include <linux/seq_file.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
-#include <linux/console.h>
 #include <linux/tty.h>
 
 #include <linux/ext2_fs.h>
@@ -175,6 +174,9 @@ void __init setup_arch(char **cmdline_p)
 	unsigned long mtd_phys = 0;
 #endif
 
+#ifdef CONFIG_DUMMY_CONSOLE
+	conswitchp = &dummy_con;
+#endif
 	cclk = get_cclk();
 	sclk = get_sclk();