[media] dvb-usb-firmware: don't do DMA on stack

The buffer allocation for the firmware data was changed in
commit 43fab979 ("[media] dvb-usb: don't use stack for firmware load")
but the same applies for the reset value.

Fixes: 43fab979 ("[media] dvb-usb: don't use stack for firmware load")
Cc: stable@vger.kernel.org
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>