staging: vt6656: [BUG] set usb_fill_int_urb interval to 1

As result of patch
staging: vt6656: [BUG] Fix Warning BOGUS urb xfer, pipe 3 != type 1

has resulted in sluggish TX performance due to interupt inverval
being too long.

Set int_interval to 1 as set in bInterval of endpoint 1.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>