staging: unisys: visorbus: Get rid of passthrough function visorchipset_bus_destroy

The function visorchipset_bus_destroy just called viosrbus_remove_instance,
we can just combine it with visorbus_remove_instance.

Signed-off-by: Sameer Wadgaonkar <sameer.wadgaonkar@unisys.com>
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>