staging: unisys: Add the bus device to the visor device list.

When the bus device was created the list_all variables were not
being initialized. When the CONTROLVM_BUS_CONFIGURE message
was being sent, it was failing to find the bus and produced a
panic. Initialize the bus_info->list_all variable by doing a
INIT_LIST_HEAD.

Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>