staging: unisys: visorbus: cleanup gotos in visorchannel_create_guts

Away label is ambiguous change to it err_destroy_channel to make it
clear this is an error path.

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