USB: cdc.h: ncm: fix one more typo

In usb_cdc_ncm_dpe32 the fields are 32 bit long and according
to usb style (hungarian notation) should be called dwDatagramIndex
and dwDatagramLength (see CDC NCM subclass spec, 3.3.2). Actually,
they were called wDatagramIndex, wDatagramLength.

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>