staging: unisys: visorbus: reorder controlvm_periodic_work

Move controlvm_periodic_work lower in the file to avoid having
to create function prototypes.

Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>