net: can: esd_usb2: Do not do dma on the stack

smatch reports the following warnings:
drivers/net/can/usb/esd_usb2.c:640 esd_usb2_start() error: doing dma on the stack (&msg)
drivers/net/can/usb/esd_usb2.c:846 esd_usb2_close() error: doing dma on the stack (&msg)
drivers/net/can/usb/esd_usb2.c:855 esd_usb2_close() error: doing dma on the stack (&msg)
drivers/net/can/usb/esd_usb2.c:923 esd_usb2_set_bittiming() error: doing dma on the stack (&msg)
drivers/net/can/usb/esd_usb2.c:1047 esd_usb2_probe() error: doing dma on the stack (&msg)
drivers/net/can/usb/esd_usb2.c:1053 esd_usb2_probe() error: doing dma on the stack (&msg)

See "Documentation/DMA-API-HOWTO.txt" section "What memory is DMA'able?"

Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Cc: Matthias Fuchs <matthias.fuchs@esd.eu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>