staging: vt6656: move local var init into declaration

Improve readability by initializing local variables at declaration.

In one instance, vnt_start_interrupt_urb_complete(), also use that
local variable in subsequent switch.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>