USB Serial Sierra: TRU-Install feature update

Moves responsbility of TRU-Install (i.e. ZeroCD) to the usb-storage
driver. See patch 04/04 of this set.

Signed-off-by: Kevin Lloyd <klloyd@sierrawireless.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>