USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()

Some values extracted by ncm_unwrap_ntb() could possibly lead to several
different out of bounds reads of memory.  Specifically the values passed
to netdev_alloc_skb_ip_align() need to be checked so that memory is not
overflowed.

Resolve this by applying bounds checking to a number of different
indexes and lengths of the structure parsing logic.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Brooke Basile <brookebasile@gmail.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>