cdc_ncm: Fix the build warning

commit 5d0ab06b upstream.

The ndp32->wLength is two bytes long, so replace cpu_to_le32 with cpu_to_le16.

Fixes: 0fa81b30

 ("cdc_ncm: Implement the 32-bit version of NCM Transfer Block")
Signed-off-by: Alexander Bersenev <bay@hackerdom.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>