vt: Initialize conswitchp to dummy_con if unset

If the arch setup code hasn't initialized conswitchp yet, set it to
dummy_con in con_init. This will allow us to drop the dummy_con
initialization that's done in almost every architecture.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20191218214506.49252-3-nivedita@alum.mit.edu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>