staging: vt6656: fix C99 // comments in main_usb.c

Resolved 'do not use C99 // comments' checkpatch errors.
Many warnings about odd indentation were left.

Signed-off-by: Andres More <more.andres@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>