usbnet/cdc_ncm: Don't use stack variables for DMA

The cdc_ncm driver still has a few places where stack variables are
passed to the cdc_ncm_do_request function.  This triggers a stack trace in
lib/dma-debug.c if the CONFIG_DEBUG_DMA_API option is set.

Adjust these calls to pass parameters that have been allocated with
kzalloc.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>