staging: unisys: visorbus: bus_configure add error handling

Add proper error handling to bus_configure and have it propagate errors
back up the stack. This helped to streamline the function as well.

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