USB: usbsevseg: fix max length

This changes the max length for the usb seven segment delcom device to 8
from 6. Delcom has both 6 and 8 variants and having 8 works fine with
devices which are only 6.

Signed-off-by: Harrison Metzger <harrisonmetz@gmail.com>
Signed-off-by: Stuart Pook <stuart@acm.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>