[media] af9015: do not use buffers from stack for usb_bulk_msg()

WARNING: at lib/dma-debug.c:947 check_for_stack+0xa7/0xf0()
ehci-pci 0000:00:04.1: DMA-API: device driver maps memory fromstack

Reported-by: poma <pomidorabelisima@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>