staging: unisys: visorbus: Consolidate controlvm channel creation.

The functions to create the controlvm channel were disjointed and ignoring
information that was available. This patch consolidates it so it clearer
what is happening.

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>